136 CLARK: THE CRINOID GENUS HOLOPUS 



It seems to me that the specimen under discussion falls very 

 little short of supplying the needed paleontological data on the 

 antiquity of maize. Its very modern appearance may of course 

 readily be interpreted as an indication of its comparatively 

 recent age, but, on the other hand, there is more than a reason- 

 able conjecture that it could be actually as old as has been sug- 

 gested, in which case it shows that the real ancestors of maize 

 must apparently be sought much earlier than has usually been 

 assumed. 



ZOOLOGY. — The systematic position of the crinoid genus Holopus. 

 Austin H. Clark. U. S. National Museum. 



The systematic position of Holopus has never been definitely 

 determined. In the latest general work on the Crinoidea^ it 

 was placed by Springer and Clark at the end of the Articulata, 

 in Family 8, Holopidae, beyond Family 7, Eugeniacrinidae, and 

 Family 6, Saccocomidae ; but this disposition was admittedly 

 provisional. 



Holopus has frequently been associated with Edriocrinus, 

 but it does not seem possible that the two can really be closely 

 related. 



In Holopus the disc, arms, and pinnules are so obviously of 

 the same type as those of the pentacrinites and comatulids that 

 the relationship with these forms can scarcely be denied. The 

 arms of Holopus are very short and thick and closely appressed 

 against each other; comparison, therefore, must be with the 

 closely appressed arm bases of such types as Endoxocrinus or 

 the genera of the Charitometridae (especially Crinometra) and 

 not with the distal portions of the pentacrinite or comatulid 

 arms, or with the widely separated arms of many forms. The 

 asymmetry of Holopus is duplicated in many of the Comas- 

 teridae. 



The disc of Holopus is identical in character with that of the 

 very young of the comatulids in which perisomic plates are 

 present — Comactinia, Comissia, Thaumatocrinus, and Pentame- 



' Zittel-Eastman's "Paleontology," 1913, p. 241. 



