1886.] NATURAL SCIENCES OF PHILADELPHIA. Ill 



The basals are so extremely large, the radials so comparatively 

 small, that the former, together with the imderbasals, frequently 

 constitute over three-fourths of the cup, while in Eupachycrinus 

 the same parts occupy not more than half that space. Besides, 

 the plates of Gromyocrinus are united by syzygy, and not by 

 ligamentous fossse, as in most species of Eiqjachycrinus. 



Our attention was directed to these facts by a species figured 

 and described by De Koniuck under the name of Eydreionocri- 

 nus (?) globularis, which in a somewhat higher degree has all the 

 characters of Gromyocrinus, and at the same time resembles cer- 

 tain forms described under Agassizocrinus. 



To Agassizocrinus have been referred two very distinct groups, 

 the one almost always without column or even columnar attach- 

 ment, with a large almost solid, subglobular or semiovoid under- 

 basal cup, nearly truncate upper side, and small basals. The 

 other, always attached to a column, with comparatively small 

 underbasals, stretched out horizontally so as to form a five-rayed 

 star, and with extremely large basals partly on the same plane 

 with the underbasals. The latter species, which include Agassizo- 

 crinus globosus and Agassizocrinus papillatus, both described by 

 Worthen, agree most closely with Hydreionocrinus (?) globularis 

 De Koninck; Poteriocrinus nuciformis McCoy ; Gyathocrinus (?) 

 sangamonensis M. and W., all previously referred by us to Eupa- 

 chycrinus, and all agree equally well with Gromyocrinus simplex 

 from Russia. These species, we think, might be arranged under 

 Gromyocrinus, and the only thing which prevented us from doing 

 so before, is the similarity with Trautschold's two other species 

 {Gromyocrinus geminatus and G. orna^ws), which in their arm 

 structure and general form approach Epachycrinus ; while they 

 agree in other points with Gromyocrinus sim2')lex. 



Gromyocrinus is closely allied to Agassizocrinus, to which it 

 holds a similar position as Pentacrinus to Antedon. We doubt 

 if Gromyocrinus QYQx became detached from its column, while all 

 species of AgassizociHnus lose their column comparatively early. 



Generic Diagnosis. Dorsal cup globular, constricted above; 

 composed of heavy plates ; sometimes (perhaps always) united 

 by syzygy. 



Underbasals comparatively large, plainly visible beyond the 

 column, horizontally arranged and forming a sharply delineated 

 star, or sometimes a very shallow cup with a slight depression for 



