Gammarus limneus. (Smith.)

Found in the Great Lakes. Dr. P. R. Hoy has found it in a clear spring brook near Racine.

G. fasciatus. (Say.)

This is doubtless the most abundant of our crustacea. I have not failed to find it, in greater or less abundance, in every stream or pool that I have examined. It is particularly numerous in small brooklets whose beds are covered with deposits of finely divided vegetable debris.

Crangonyx gracilis. (Smith.)

This species has not been found in the interior waters of the state. It occurs in Lake Superior, and Professor Forbes finds it in abundance in central Illinois.

Asellus intermedius. (Forbes.)

Abundant in stagnant sloughs and slow running brooks about Sauk City. These Wisconsin specimens differ from the types of Professor Forbes in several unimportant details, especially in the shape of the ramus of the first genital plate, and the size of the second joint of the inner ramus of the second plate.

Assellopsis tenax. (Hagen.)

This species I have not seen. It is reported from Lake Superior. Eubranchipus bundyi. (Forbes.) Bulletin No. 1, Ill. Mus. Nat. Hist., 1876.

This, our largest phyllopod, was discovered in small ponds of sur face water at Jefferson. It was found in abundance in April, but after a few weeks entirely disappeared. Specimens found in two neighboring ponds, while indistinguishable in other respects, differed markedly in size and coloring. In one of these ponds in a densely timbered lot they were small, and pale in color, while in a pond exposed to the sun they were much larger and brilliantly colored.

Limnetis (sp.?)

In company with the smaller Eubranchipides above mentioned was found an apparently undescribed species of Limnetis. have met with it in no other locality.

Dioptomus sanguineus. (Forbes.)

This beautiful little creature is an abundant inhabitant of the marshy pools and ditches near Sauk City.

THE CORALS OF DELAFIELD.

BY IRA M. BUEL.

The large collection of fossils made by the Geological Survey at Roberts' quarry, Delafield, Wisconsin, is surpassed in interest and scientific value by no other representation of Paleozoic fauna ever obtained from our state. It contains thousands of specimens almost perfectly preserved by the blue friable shale in which they were imbedded; and of the seventy species already distinguished, about one-half are new to science. The coralline representatives found here are of special interest to the student and naturalist.

The locality in question (Sec. 21, T. 7, R. 18 W.) lies on the southern shore of Pewaukee lake, and in the edge of a trough carved by glacial forces out of the lower layers of the Niagara limestone, and the soft underlying Cincinnati shales; the basin being occupied in part by the lake itself. By the removal of the limestone layers in the quarry, quite a surface of this shale was exposed, and as this formation somewhat resembles some of the Carboniferous shales, it was supposed by some inquiring mind to belong to that formation. A shaft was accordingly sunk at this point for the discovery of coal, and was not abandoned until a depth of fifty feet had been reached. The mound of rock and clay thrown out of this pit or shaft, the rain-washed monument of a geological delusion, was the source of all of the specimens obtained from that locality.

These corralline forms are all of small size, the smallest species measuring about an inch in length and about a tenth of an inch in diameter. The largest coral fragment is about two inches in diameter and consists of a sort of central base from which a number of slender arms branched out. Within these limits we find almost every possible variation in form, manner of growth, branching and surface markings.

The size, form and arrangement of cells and cell walls, are the principal distinguishing features of these corals; and as these features are mainly microscopic, the labor of identification of species and varieties among these thousands of specimens was not a small

task. The Polyp or Bryozoan cells seldom exceed a hundredth of an inch, and in some species are less than a two hundred and fiftieth of an inch in diameter. The cell walls and interspaces are often dotted with pits or pores, the tubuli of some authorities, or studded with granules, whose dimensions are from one-half to one-tenth of the diameter of the cells. In the illustrated drawings these surface markings are enlarged from twenty to fifty diameters.

The term corals, as applied to these forms, does not necessarily imply that they belong to the radiate sub-kingdom. We find, indeed, that Professor Dana includes under this general term calcareous or honey structures formed not only by Polyps and Hydroids (Radiates), but by Bryozoans (Mollusca), and also by certain low vegetable forms.

In the classifications that have been made, the widest diversity exists; no two authorities seem to agree, and the same species is relegated even to different sub-kingdoms by leading naturalists. Of the thirteen genera recognized in this collection, Professor Whitfield has placed Chatetes, Monticulipora, Stellipora, Alveolites and Dekayia under Corals; and Trematopora, Fistulipora, Palaschara, Stictopora, Fenestella, Retopora, Alecto and Aulopora under Bryozoans. S. A. Miller, of Cincinnati, classes the first group as Radiates of the Favosite group, Fistulipora as a Millepore, Aulopora as an Aleyanoid coral, and the remainder Bryozoans. Professor Dana differs from others in considering the Chcetetes and related genera Hydroids instead of Polyp corals, while Dr. Rominger, of Michigan, throws them out of the Radiate sub-kingdom altogether, and places the whole list under Bryozoans. The close relationship and gradation of forms observed in our specimens indicate that they should not be separated into as widely differing divisions as has heretofore been done.

Before considering this matter further, we will notice the relationships that exist between some of these forms. Beginning with those genera that are considered by all authorities as belonging to the Bryozoan order of Mollusks, we first notice the two representatives of the genus Stictopora, that are found in this collection. (Fig. 1 represents S. elegantula, and Fig. 2 S. fragilis.)

The genus is thus described by Dr. Hall: "A foliaceous branch. ing coral, supported by smooth rootlike expansions; branches bifurcating and sometimes coalescing, celluliferous on both sides, with thin central axis. Cellules, oval tubes, not enlarged below apertures, distinctly oval with raised borders, nearly as wide as the cells within.

The distinctive features of these species lie in the mode of branching, size, shape and arrangements of the cells. Their resemblance to modern Bryozoan forms is manifest. This resemblance is still more plainly seen in the reticulated forms represented by Figs. 3 and 4. These are incrusting forms with the cells on

1 These figures refer to drawings placed before the association at the presentation of this paper in December, 1878. Some of the corals will be illustrated in Vol. IV, Wis. Geol. Surv.

one side only. Fig. 3 is an undescribed species, referred to the genus Retopora by Professor Whitfield. Fig. 4 was described by Professor Whitfield, and his description is found in the annual report of the Wisconsin Geological Survey for 1877, p. 68, under the name Fenestella granulosa.

The more obvious characters of each form are as follows: The Retopora presents anastomosing branches with irregular, elliptical or linear, pointed meshes, upper surface of branches thickly covered with circular pores which are arranged in three or four longitudinal rows. In the Fenestella the branches do not reunite after separation, but frequently bifurcate and are connected at quite regular intervals by extremely narrow bars which divide the interspaces into oblong spaces or fenestrules. The pores in this form are arranged in lines, a single row on each margin of the branches or rays. The opposite surface of the frond is densely covered with very minute granules, hence the term granulosa, applied to the species.

Turning to those forms which more closely resemble living radiate corals, we notice first of all the delicately formed Trematopora annulifer, Whitfield, described in the Annual Report Wisconsin Geological Survey for 1877, page 67. Scores of fragments of this beautiful fossil are found imbedded in

the surface of some of the blocks of shale, and though their diameter is hardly larger than that of a knitting needle, their peculiar sharp annulations distinguish them at a glance. The surface pores are fine as needle points, yet under the microscope show in general an elliptical section and are separated by grooved walls giving to each opening a distinct margin or rim which is elevated into a sharp spine on the lower side. The genus Fistulapora exhibits a still further remove from the Bryozoan type. The larger cells in this series have plainly marked transverse partitions as in the Favosite corals. Still we have in some forms thin incrusting layers and masses built up by the superposition of these layers. Our collections contain several new species of this genus, two of which have been described. The two forms to which I wish to call your attention now are F. solidissima and F. lens. The surface markings in these species are nearly alike; the former presents solid, cylindrical or flattened stems, often branching, while the latter presents disk-like expansions with openings on one side only. The surface of the former shows very small elliptical cells, separated by comparatively thick walls or interspaces which are studded by minute pores arranged in one, two, or sometimes three rows between the cells. Twelve to sixteen of these larger cells are found in the space of an eighth of an inch, measured along the branches. In F. lens the cells are rather larger and the interspaces narrower; otherwise the appearance of the surface in these species is similar.

The forms already noticed are generally considered to be Bryozoans. The difference of opinion that has been referred to applies principally to the remaining forms, and at this point, therefore, we should look for some important fundamental distinctions.

The genus Stellipora stands nearest to those just noted, and, therefore, claims our attention. The beautiful form, S. polystomella, is one of our most common fossils; and although we obtain only fragments of its broad frond-like expansions, the star-like tubercles that stud its surface, when perfectly preserved, render it one of the most attractive species to the casual observer. Our species is identified with the form described by Nicholson in the Ohio reports, but presents some points of difference. This