1881.] NATURAL SCIENCES OF PHILADELPHIA. 293 



moment as sufficient for generic separation, as liad been proposed 

 in the case of Ctenocrinus Bronn,' those plates are mere acces- 

 sory pieces, and may be present or absent in the same species. 



Turhinocrinites Troost was proposed in MS. (according to 

 Hall) for a species which was said to have the first anal plate in 

 line with the first radials, but Troost's typical species Melocr. 

 Verneuili, which was subsequently defined by Hall, seems not to 

 have possessed such a plate, as Hall himself mentions expressly 

 that the anal area is but slightl}' distinct from the regular inter- 

 radial ones. 



Cytocrinus Roemer was described b^ its author with probably 

 three (?) basal plates — the exact number had not been ascertained. 

 A good specimen in our collection from Louisville, Kj'., which in 

 every respect agrees with G. Isevis Roemer, shows that it has four 

 basals, and that the genus is identical with Melocrirma. Roemer 

 himself gave for locality both Western Tennessee and Louisville. 



Phillipsocrinus McCoy, which was described with four basals, 

 has been frequently connected with Melocrinus. The generic 

 description was made from a single specimen, and this was evi- 

 dently abnormal, as indicated by having two additional plates in 

 line with the first radials (seven in all), and we think it probable 

 that the abnormal seventh plate in this case rendered the presence 

 of the fourth basal plate necessary. We take it to be an abnormal 

 specimen of Actinocrinus, and this is far more consistent with the 

 given geological position. 



Generic Diagnosis. — Body obconical, subglobose or pear- 

 shaped, with five free rays extended upward and giving oflT arms 

 laterally. Cah'^x highly ornamented with radiating ridges, some- 



^ The genus Ctenocrinus was at first incorrectly defined. It was des- 

 cribed by Bronn iJalirbuch, 1840, p. 542) witli three basal plates, which 

 was confirmed by Roemer ( Leth. Geogn., 1855, p. 251 ), and subsequently 

 de Koninck considered the genus identical with Pradocrinus de Verneuil 

 (Criu. du terr. Carb. Belg., p. 147). Job. Midler (Verhandl. naturh. 

 Verein, 1855), admits more than three basals, i^robably five, and in 1857 

 (Neue Echin. Eifel Kalk, p. 255), he mentions positively five basals, and 

 compares Ctenocrinus with Glyptocrinus Hall, asserting that it had also 

 parabasalia. Schultze afterwards in his Monograph, p. 63, proved fi-om 

 more perfect specimens that Ctenocrinus typus has only four basals and no 

 underbasals, which is evidently correct. One of us had an opportunity 

 several years ago to study the Schultze collection in the Museum of Com- 

 parative Zoology of Cambridge, which contains specimens showing only 

 four basals like Melocrinus. 



