NATURAL SCIENCES OP PHILADELPHIA. 163 



extend out nearly horizontally pentagonal in outline, and each supporting on 

 its superior lateral sloping margins the first divisions of the arms, which are 

 comparatively small and bifurcate again on the second piece ; beyond this the 

 two outer divisions remain simple, but the two inner divide again on the second 

 piece, making six arms to each ray, or thirty to the entire series. Arms after 

 the last divisions long, slender, cylindrical, and composed at first of a simple 

 series of quadrangular pieces, but passing gradually upwards into interlocking 

 triangular pieces, and still farther up forming a double series of small alterna- 

 ting cuneiform pieces, supporting closely arranged, long-jointed tentacles. 

 Anal, interradial, and vault pieces unknown. Sutures, excepting between the 

 basal pieces, distinctly, but not widely or deeply channeled. 



Surface ornamented with rather small, but well denned, prominent nodes. 

 On the base, tnese nodes are arranged in ten rows, five of which radiate 

 from the columnar facet, one to each of the corners ; while those between each 

 of these form intermediate radiating rows, consisting at first of a single range, 

 but becoming a double or triple range near the margin, when the three some- 

 times coalesce laterally. On the first radial pieces two rows pass from just 

 beneath the facet for the reception of the second radials, to each of the inferior 

 lateral angles, while between these there is, at first, a single node, but farther 

 down two or three rows, consisting of nodes which show a disposition to 

 elongate, or coalesce laterally, so as to form little transverse ridges. Above, 

 there is also a row extending horizontally to each superior lateral angle, with 

 a few less regularly arranged nodes on the sides below these. A single trans- 

 versely elongated node sometimes also occurs on the little radials, and one 

 less distinctly defined also sometimes on each of the pieces between this and 

 the next bifurcation. 



Breadth of body at summit of first radial pieces, 1-07 inches ; height of do. 

 0-60 inch ; breadth of base 067 inch; breadth of second radial pieces at the 

 summit, 0-54 inch ; do. of second radials, 0-19 inch. 



From the description, it will be seen this species is rather closely related 

 to P. granulatus of IMiller, which it nearly resembles in form and general ap- 

 pearance. It is a larger and more robust species, however, and differs, not 

 only in the arrangement of the pustules on the base into distinct radiating 

 rows, but according to Austin's figures and description (Monogr., Recent and 

 fossil Crinoidea, p. 33, pi. 3, f. 2,) in having but six instead of seven arms to 

 each ray, as well as in having the arms above the middle composed of a double 

 series of small wedge-shaped pieces, instead of consisting of a single series 

 throughout. From its analogy to P. granulatus, of Miller, it will probably be 

 found to possess, like that species, a long subcentral proboscis. 



Locality and position. Crawfordsville, Indiana. Keokuk division of Sub- 

 carboniferous Series. 



Platycrinus parvulus, M. and W. 



Body very small, short subcylindrical, or deeply cup-shaped. Base depressed 

 basin-shaped, or several times as wide as high, columnar facet about one third 

 as wide as the base, with a small marginal rim. First radial plates nearly ob- 

 long, being longer than wide, with nearly parallel sides ; some of them with 

 two obscure linear ridges extending from the middle of the upper side, and 

 slightly diverging to the base ; each moderately concave above for the recep- 

 tion of the next range of pieces. Second radial pieces very minute, about 

 twice as wide as long, but not equalling the breadth of the slight concavity in 

 the upper side of the first radials. Third radial pieces, slightly wider than the 

 second, and about of the same length, pentagonal, and each supporting an arm 

 on each superior sloping side. Arms each dividing on the second piece be- 

 yond which they are simple, at least for four or five pieces above, and com- 

 posed of a single series of quadrangular pieces, about as long as wide, ex- 

 cepting the first, which is near twice as long as wide. Tentacles apparently 



1865.] 



