said above, has with the bifurcations 8 X 5 = 40. D. cornigerus which differs considerably from all other species, has 4 × 5 = 20. D. ficus has six pairs, 6 X 2 = 12, again bifurcating on the first joint, producing twenty-four arms or fingers. We may readily suppose that the greater number of the species of this genus have five pairs of arms, bifurcating once or more. The arms are long, fimbriated, and composed of cuneiform pieces, either in single or double

rows.

Inter-radials. Shumard is the only author who notices inter-radials. He says, that "from four to five exist in two of his species, they rest on the oblique superior lateral edges of the radial plates." They might easily be mistaken for the lower pieces of the vault.

We propose, then, the following formula for Dichocrinus:

The vault, in all the specimens where we have seen it preserved, is large, high, and more or less ornamented with thorns and salient tubercles. This genus differs so markedly from the genera Platycrinus and Hexacrinus, both in the more elongated form, the bipartite basis, and its deep angular notch on the anal side, that it admits of an easy distinction. It approaches quite nearly to Cotyledonocrinus and Pterotocrinus, having like them a bipartite base, with a series of large pieces about it. Cotyledonocrinus has only five pieces arising from the basis, instead of six, the arms are non-bifurcate; the difference between this genus and Pterotocrinus is so marked that they cannot be confounded.

DICHOCRINUS POLYDACTYLUS, Sp. Nov.

Body. Subconoidal, resembling the ornate capitals of some composite columns, spreading rapidly from the base, the upper portion marked by prominent folds of salient tubercles. The whole of the pieces of the calyx are thin.

Vault. Surmounted by a large proboscis: column small, subrotund. Basal pieces. The two basal pieces are large, spreading rapidly

from a small base, similar in size, obscurely heptagonal; at the terminations of the diameter opposite from the one which makes the suture line they are prolonged into quite acute angles, forming the two obscure angles of the heptagon. Immediately above the columnar pit, or a very little below it, is a series of massive tubercles irregularly disposed, and varying in size, the remainder of the bases being comparatively smooth. From the margin of the columnar pit extend, in the direction of the arms, four raised folds, two on each piece, ornamented by several tubercles and striæ.

Radials. The first are very large, pentagonal, trapezoidal in shape, their upper facets being much wider than the lower ones. They extend out as far as the first or second pieces beyond the axillary radials; the middle portions are swollen out into folds or plaits; their junction with the second radials is distinguished by a large tuberous knob, beneath which are one or two smaller ones. A number of striæ regularly disposed, and a few minute granules are scattered over the surface of the pieces. This raised median line of the radial pieces produces broad intervalla between each two of them. The second and third radial pieces are very minute; the second join the first radials at the knobby prominence described above; the third are axillary, and give off two rays each.

Inter-radials. One large inter-radial is placed between each pair of arms.

Anal piece. At one termination of the articulating facet of the basal piece (the other being at the anterior radial piece) is situated a single anal piece. It is not so wide as the radials, but of the same length, pentagonal; as in the radials, its centre is elevated, it differs from them in the portion where the second radials join the first; on the radials there is a well-defined, articulating facet, whilst on the anal piece none exists, the piece being solid and continuous throughout.

Vault. We have no specimen showing the vault; in one example before us, there is a proboscis much crushed and misshapen; it is large, composed of many small, coarse, tubercular pieces, and extends not quite one third the length of the arms. Its terminal point is apparently formed by two circles of pieces surrounding a single one.

Arms. From each third radial come off two arms. They are about three times as long as the body, and arranged as follows: in each arm six quite stout quadrangular pieces, rounded on the dorsal surface, are superimposed upon each other; the sixth are axillary,

each give off two slender fingers, which are composed of the following pieces: first, one or two quadrangular ones, upon them from five to seven somewhat smaller wedge-formed ones placed one above another, the large end of one wedge being placed over the small end of the next, the wedges becoming gradually more acute, until on the sixth or seventh piece there commences a double row of small, quite acute, pentangular pieces, which alternate with each other, the salient edges of one row fitting into the retreating angles of the other row, the points of their junction being lateral, not central, as in most other genera having similar arms. Yet two more fingers exist on each arm; they are situated on the outer surfaces of the six pieces described above (the first one on the second piece from the last radial, the second one on the fourth piece from the same radial), the inner surfaces having no branches, and lying close together throughout their whole extension. They spring apparently from the sides of the pieces, the facets being on the sides, rather than on the top as in a regular axillary piece; curving out gracefully for a short distance, they continue in a straight line to their ends without any further bifurcation. They are slender, composed of pieces exactly similar to those of the fingers already described. On either side of the ambulacral grooves of the fingers is a row of stout pinnulæ.

.60

66

Length of proboscis (variable proportion in diff. sp.)

Geological Position and Locality. Rare in the silicious mud beds at the top of the Knob member of the subcarboniferous limestone, Hardin County, Kentucky; Montgomery County, Indiana, &c.

DICHOCRINUS SYMMETRICUS, Sp. Nov.

Body. The general form of the body is subconical; from the basis to the summit of the first radials it is basin-formed, above which it contracts upward and terminates in a point, formed by the large spinous piece which surmounts the vault.

The basal pieces, two in number, are of equal size, pentagonal; line of junction with each other straight, forming when united an irregu

larly-sided octagon. The columnar pit is shallow, oval; columnar facet obscurely pentagonal; perforation small and round. The pieces are prominent near the line marking their junction to those resting upon them, being suddenly reflected upward.

Radial pieces five, subquadrangular, the largest as wide as high, diminishing in size from the anterior piece on either side to the anal piece, swelling from the base and sides toward the superior margin, irregularly truncated above, slightly depressed at the summit between the pieces.

Second radials. Fragments of the second radials are attached to some of the first radial pieces; they are minute, and rise within the superior margin of the first radial pieces. The precise form of the second radials is not known.

Inter-radials. Between each group of arms, resting in the depression between the radials, is a single piece, usually pentagonal in form; it rises nearly as high as the opening into the body at the arms.

Anal pieces. Rising from the deepest angular notch at the junction of the basal pieces, is a large piece, the lower part of which is similar in form to the first radials, rising higher than they do; the upper margin is horizontally truncated about one third the breadth of the piece; the sides above the radials angularly sloping toward the top of the radials on either side; the centre of this piece supports one, and the sloping sides each support a piece of the second range of anal pieces; those on the sides correspond in size, form, and position, to the inter-radial pieces above described. These are again succeeded by a third range of pieces, triangular in form, three in number, the central one of which reaches the mouth (?), which is surrounded by three additional, small, long, narrow pieces. The series of pieces under the mouth are slightly depressed above the second range.

Summit. The summit above the radials recedes a considerable distance within the upper margin of the calyx. It is covered by numerous small polymorphous pieces, six of which are spinigerous; the largest and most prominent of these occupies the centre of the summit, immediately in contact with the pieces surrounding the mouth; the other pieces forming the second series of those rising above the openings into the body at the arms. The two spinous pieces above the arm-pieces of the postero-lateral rays form a circle around the central piece, the anterior part of the summit having one more range of pieces above the arms than above those arms on either side of

the anal field. Beneath each of the small spinous pieces above the arms is a pentangular piece, the inferior margins of which are prolonged into an acute angle, separating the openings into the body into two equal parts, the upper portion of these pieces supporting the spinous pieces above the arms, the lateral upper portion supporting a piece on either side: these last pieces are prolonged downward, and curved around the outer sides of the arm openings, the outer margins of those touching each other form a closed ring, with the piece between them around the summit, except on the anal side. The lower margins are supported on either side by the upper margin of the inter-radial pieces. On the anal side are two additional pieces, nearly square, resting between the last pieces above described and the spinous pieces, and the pieces described above as anal pieces.

Arms. The openings into the body are five pairs; the arms are in all, probably, ten in number: their form is unknown.

Column. Unknown. We are indebted to Professor J. M. Safford, of Tennessee, for the beautiful specimen figured in his report.

Geological Position and Locality. Rare in the upper beds of the cavernous member of the subcarboniferous limestone, in Breckinridge, Grayson, Edmondson, Hart, and Warren Counties, Kentucky. Vertical range, so far as at present known, about sixty-five feet, reaching from the base of the first sandstone of the millstone-grit beds to the first white bed beneath.

DICHOCRINUS ELEGANS, Sp. Nov.

Body. Viewed from above the outline of the summit is stellate; the deep grooves between the arms and the anal side would produce a sinuous stellate figure in any section above the calyx. The calyx is somewhat basin-shaped, but it is much more erect than in D. symmetricus. The rounded form of the first radials is continued to the top of the second piece above the arms, dividing the body into five prominent ridges.