2 CATALOGUE OF THE BLASTOIDEA. 



he never included it in his family Crinoidea, to which it has been so often referred 

 by his successors. It has a jointed column which supports a cup-like body containing 

 the viscera, just as in Platycrinus ; but this cup bears no arms, and it is clear that 

 their absence was regarded by Miller as a sufficient reason for not including the 

 Pentremite type among the Crinoidea. 



Say 1 remarked in like manner: — "By its columnar support it is related to the 

 family Crinoidea, but the total absence of arms and hands excludes it from that very 

 natural group ; " and he therefore described the Blastoids as a new family of Echino- 

 derms occupying an intermediate position between the Crinoidea and the Echinoidea, 

 with which last group he imagined Pentremites to have some affinities. This was 

 perhaps due to his thinking it highly probable that " the branchial apparatus com- 

 municated with the surrounding fluid through the pores of the ambulacra? by means 

 of filamentous processes " 2 . 



Later researches have shown, however, that Say and many subsequent writers were 

 almost certainly wrong in this supposition. But while the imaginary affinity of the 

 Blastoids with Echini has thus received a certain amount of support, their funda- 

 mental difference from the Crinoid type has been in no way lessened ; and the results 

 of recent investigations into the structure of both groups fully bears out Say's 

 remarks upon the subject. 



His description of the " Kentucky Asterial Fossil," under the generic name Pentre- 

 mite 3 , led to the establishment of several new species duriug the next twenty-five years 

 by Sowerby, Phillips, and M'Coy in this country ; by Bronn, Goldfuss, De Koninck, 

 Miinster, and De Verneuil in continental Europe ; and by Troost, Yandell, and 

 Owen and Shumard in America. A new generic type was recognized by Troost and 

 by Conrad in America (Olivam'tes, Troost, MS., =NucIeocrinus, Conrad, =Elceacriaus, 

 Roemer 4 ) ; and another, which was recognized by Conrad and described by himself 

 and by Hall 5 under the name of Stephanocrinus, was placed by Ferdinand Roemer 6 

 among the Cystidea, a proposal in which we cannot agree. In. this country, too, 

 Astrocrinites and Codaster were described by the Messrs. Austin 7 , and M'Coy 8 



1 Loc. cit. p. 292.- 2 Ibid. p. 296. 



3 " Observations on some Species of Zoophytes, Shells, &c., principally fossil.'' American Journ. Sci. 1820, 

 vol. ii. p. 36. 



1 " .Monographie der fossilen Crinoidenfamilie der Blastoideen, und der Gattung Pentatrematites im 

 Besondern." Archiv f. Naturgeseh., 1851, Jahrg. xvii. Bd. i. p. 375. 



5 Pakeontology of New York, vol. ii. (Albany, 1851), p. 212. 

 •' Ueber StepTianocrinus, eir.e fossile Crinoiden-Gattung aus dor Familic der Cystideen.'' Archiv f. 

 Naturgeseh. 1850, Jahrg. xvi. lid. i. pp. 365-375, Taf. v. 



" Proposed Arrangement of the Echinodermata, particularly as regards the Crinoidea, and a subdivision 

 o the Class Adelostclla (Echinida;)." Ann. & Mag. Nat. Hist. 1842, vol. x. p. 112. 



e "Ou some new Palaeozoic Echinodermata." Ibid. 1849, vol. iii. p. 250. 



