EcuiInopERMATA. | UPPER PALAOZOIC RADIATA. 123 
Copaster acutus (M°Coy). Pl. 3. D. fig. 7. 
Ref—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. III. p. 251. 
Sp. Ch.—Pelvie and supra-basal plates of equal length; pelvis acutely conical, obtusely subtrigonal in 
section; columnar adherence small, round, prominent; surface smooth. Length six lines, width of disk five 
lines. 
Position and Locality—Not very uncommon in the carboniferous limestone of Bolland. 
Explanation of Figure.—P\. 3. D. fig. 7. Profile of specimen, natural size, 
CoDASTER TRILOBATUS (M°Coy). Pl. 3. D. fig. 8. 
Ref—M ‘Coy, Ann. Nat. Hist. 2nd Series, Vol. III. p. 251. 
Sp. Ch.—Supra-basal one-third longer than the basal or pelvic plates; pelvis divided into three tumid 
lobes which hang below the columnar adherence; surface smooth. Length seven lines, width of disk five lines. 
Position and Locality —Not uncommon in the carboniferous limestone of Derbyshire. 
Explanation of Figures.—Plate 3. D. fig. 8. Profile of specimen, natural size.—Fig. Sa. End view of 
truncated summit of ditto, magnified. 
Genus. PENTREMITES (Say). 
Gen. Char.—Pelvis small, pentagonal, of five pentagonal pieces, supporting five large pentagonal supra- 
basal pieces or scapulie, each of which has a long narrow fissure from the apex nearly to the base, to receive 
the ends of the pseudambulacra* ; in the upper re-entering angles of the plates are five large ovarian pentagonal 
plates, the apices of which converging towards the vertex close the cup, leaving at their junction a small central 
mouth; a narrow space intervenes, between each pair of these plates, for the pseudambulacra, and each is 
pierced at its apex by an ovarian foramen, one of which is much larger than the rest; pseudambulacra of two 
rows of very minute pentagonal plates, one oblique pair of pores (sections of alimentary canals) in each row. 
I think I observe ocular pores at the oral ends of the pseudambulacra, in which case they would be in an 
abnormal position, though as usual beside the ovarian pores; these latter, it will be remarked, resemble those of 
the Echinide in structure, but those of the star-fishes in position. Before M. Yondell’s discovery of the rows of 
fingers on the pseudambulacra of the American Pentremites it had struck me that these latter could not really 
be ambulacra as was supposed, because instead of being lodged in the sutures between the so-called scapule, 
they were each received in a deep notch down the middle of those plates,—a position which is obviously iden- 
tical rather with that of the arms of true Crinoids. 
PENTREMITES CAMPANULATUS (M‘Coy). PI. 3. D. f. 9. 
Ref —MCoy, Ann. Nat. Hist. 2nd Series, Vol. III. p. 249. 
Sp. Ch.—Bell-shaped, base as wide as the body; pseudambulacra wide above, tapering to the angles 
at the base; transverse sutures between the first and second series of supra-basal plates nearly medial; base 
flattened ; surface minutely granulated. Length three lines, width three lines. 
If we suppose the lower third abruptly cut off a P. edlipticus we should have a good idea of the shape 
of this little species, which, agreeing with the above in most characters, is distinguished by its small size 
more tapering ambulacra, greater proportional width, and wider base. 
* T have used the word pseudambulacra to designate those poriferous rows in Pentremites, &c., which resemble 
ambulacra, but the pores of which are found by MM. Roemer and Yondell (Bulletin de la Soc. Géol. de France, for 
April 17, 1848) to be really the alimentary canals of a double row of little jointed tentacles resembling, I imagine, those 
of Pseudocrinites. 
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