Oct., 1907. New Crinoids — Slocom. 287 



Order IT. FISTULATA. 



Family GASTEROCOMID.^. 



ACHRADOCRINUS Schultze. 



This genus was originally proposed by Schultze, to receive a species 

 from the Devonian rocks of the Eifel, Germany. The species collected 

 by the writer and here described is the first American species to be 

 referred to the genus. The original description* of the genus is as fol- 

 lows : "The composition of the calyx is as follows : Basalia (infrabasals) 

 five, equal, pentagonal; Parabasalia (basals) five, four equal, pent- 

 agonal, the fifth hexagonal; Radialia (radials) five, pentagonal, alter- 

 nating with parabasalia (basals) ; Interradials (anal plate) one, resting 

 on the horizontal, truncated edge of the hexagonal parabasal (basal) 

 directly beneath the anal opening. 



Ventral dome, arms and column unknown. The base is pierced 

 by a single circular canal." 



Genotype Achradocrinus ventrosus. 



To the above description of the radial plates may be added the 

 following, as the characters are generic : Radials five, shield-shaped ; 

 three regular and equal, the two posterior 

 ones irregular, deeply excavated for the 

 reception of the anal plate which they en- 

 close on three sides by meeting above. A 

 prominent articular facet occupies the 

 outer side of the radials near their distal 

 edges. The facets are provided with a 

 ventral groove and are pierced by a small 

 canal located at some distance from the 

 groove. 



In referring Achradocrinus to the Gas- blgb - D ' a f ran I °! ****** 



° (After Schultze). 



terocomidae Schultze compares it with 



Gasterocoma, which it resembles in general arrangement of the plates 



and position of the anal interradius, but from which it differs in the 



form of the basal canal. In Gasterocoma the base is pierced by 



a quadrilobate canal and in Achradocrinus by a circular, central 



canal. 



So far as is known to the writer, all genera heretofore referred to 

 the Gasterocomidae have been of Devonian age. 



♦Monographic der Echinodermen des Eifler Kalkes, p. 101. 



