1886.] NATURAL SCIENCES OP PHILADELPHIA. 65 



chavacteristic of the whole group, though it may vary in degree, 

 and is probably far less perfect in some genera than in Forbesio- 

 crinus and Onychocrinus. 



Zittel (Handb. d. Palseont., i, p. 353-5-6), has separated the 

 genera which belong to this suborder into three families, viz.: = 

 Taxocrinidae, including: (A), Taxoc7'inus, Forbesiocrinus, Ony- 

 chocrinus, Gissocrinus, 3Iyelodactylus ; (B), Lecythocrinus (?), 

 Dactylocrinus {Dimerocrinus Pictet); Ichthyocrinidae, includ- 

 ing : Bomalocrinus, Lecanocrinus, Clidochirus, Mespilocrinus, 

 Ichthyocrinus, Anisocrinus and Pycnosaccus; Crotalocrinidse, 

 including Crotalocrinus, Enallocrinus, Gleiocrinus. Angelin 

 refers Taxocrinus, Forbesiocrinus, Gissocrinus and Myelodactylus 

 to the Taxocrinidse ; Ichthyocrinus and Pycnosaccus to the Ich- 

 thyocrinidffi ; Crotalocrinus to the Crotalocrinidse and Enallo- 

 crinus to the Enallocrinidae. 



The so-called genus Myelodactylus may be left out of consider- 

 ation. It was founded upon columns only, and, if correctly 

 identified by Angelin, which is improbable, it would not belong 

 to the Articulata at all. A separation of the genera included by 

 us in the Ichthyocrinidse into two families is desirable, but all 

 attempts to define satisfactory characters for such families have 

 so far failed. We have tried to arrange them according to Zittel's 

 definition as well as various plans of our own, but without success, 

 and we have come to the conclusion that the separation must be 

 based upon characters as yei undetected. It is a remarkable and 

 perplexing fact that in this whole group such characters as the 

 presence or alisence of interradials dorsally, the number of pri- 

 mary radials, or the position of the anal or azygous plate, whether 

 resting on the basals or not, seem to be of little value. 



Until some new light shall be obtained we see no other course 

 than to leave the family Ichthyocrinidse as we have already 

 defined it. 



Gissocrinus, which is placed by Angelin and Zittel among the 

 Taxocrinidse on account of having three underbasals, belongs to 

 the Fistulata, and has been referred by us to the Cyathocrinidae, 

 as have also Lecythocrinus and Dactylocrinus. In addition to 

 the genera formerly included by us, we refer C yrtidocrinus to 

 the Ichthyocrinidse. 



Gleiocrinus was independently referred by Zittel to the Crota- 

 locrinidse, and by us to the Ichthyocrinidffi. It differs from all 



