1886.] NATURAL SCIENCES OF PHILADELPHIA. 115 



crinus there are several which range infinitely lower than others, 

 and these should be placed under new genera. 



The azygous side of the Cyathocrinidae consists rarely of more 

 than two plates in the calyx the azygous plate and the anal 

 piece ; but the Poteriocrinidte generally have three, owing to the 

 fact that the first plate of the ventral tube extends often into the 

 calyx. The ventral sac is perhaps more club- or balloon-shaped 

 in the Poteriocrinidae, more cylindrical in the Cyathocrinidae. 

 We subdivide the C3'athocrinid8e into : 



Dendrocrinites, genera with a large azygous and well-developed 

 anal plate, embracing : Merocrinus, Carabocrinus, Dendrocrinus, 

 Homocrinus, Ampheristocrinus and Farisocrinus. 



BoTRYOCRiNiTES, genera having no special azygous plate or 

 occasionally a rudimentary one, and armlets in place of pinnules: 

 Atelestocrinus, Vasocrinus, Botryocrinus, Sicyocrinus, Streblo- 

 crinus and (?) Barycrinus. 



Cyathocrinites, genera without azygous plate, with branching 

 arms without pinnules : Gyathocrinus, Arachnocrinus, Gisso- 

 crinus, Sphaerocrinua^ Achradocrinus^ Godiacrinus and (?) 

 Lecythiocrinus. 



Zittel placed Gissocrinus among the Taxocrinidae, tlie perfectly 

 symmetrical Godiacrinus among the most unsymmetrical Gastero- 

 comidae, and Ophiocrinus, Dendrocrinus and Homocrinus, which 

 are devoid of true pinnules, among the Poteriocrinidie.^ 

 We subdivide the Poteriocrinidae as follows : 



PoTERiocRiNiTES, genera having an azygous plate, a regular anal 

 piece, and the first plate of the ventral sac enclosed in the calyx : 

 Foterioo'inus, Scaphiocrinus, Scytalocrinus, Decadocrinus, Woodo- 

 crinus, Zeacrinus, Hydreionocrinus, Gceliocrinus, Eiipachycrinu:<, 

 Gromyocrinus and Tribrachiocrinus. 



Graphiocrinites, genera without azygous or anal plate, but 

 the first plate of the sac within the limits of the calyx : Graphic- 

 crinus, Bursacrinus^ Phialocrinus and Geriocriniis. 



Erisocrinites, genera without azygous or anal plate dorsally : 

 Erisocrinus and Stemmatocrinus. 



^ Prof. Zittel figures, Handb. d. Palaeont., i, p. 359, as type of the Poterio- 

 crinidae a species devoid of pinnules. Poteriocr. curtus Miiller, is evidently 

 a Hornocrinus. 



