208 PROCEEDINGS OP THE ACADEMY OF [1886. 



and he certainly did not describe arabulacral appendages, but 

 branching fingers, no matter what name he gave to the parts. 

 We are confident that the depression at the end of the ambula- 

 cral groove really does exist, and that it is occupied by a second 

 radial. 



Stephanocrinus not onl^^ has two radials to each ray, but 

 branching biserial arms, given off in a somewhat similar m:inner 

 as the arms in the Platycrinidse. The second radials are reni- 

 form, small, bifurcating, and rest within a semi-ovoid or horse- 

 shoe-shaped depression near the outer end of the ambulacral 

 groove. They are succeeded b}'^ two or more axillaries of a 

 higher order, which in the usual way give origin to ten arms to 

 each ray. That these appendages, although they are equall}'^ thin 

 and short, are not pinnules, is proved by the fact that all are 

 supported hy a radial plate, instead of being distributed sepa- 

 rately along the sides of an ambulacrum. It is further shown by 

 one of the New York specimens, in which in one of the raj'S the 

 appendages became disconnected, and were deposited en masse 

 at some little distance from the radials, without the least disturb- 

 ance in their arrangement, a case which could not have happened 

 if they were ambulacral pinnules. 



The ambulacra of Stepkanocriiius are constructed very differ- 

 ently from those of the Blastoids ; they possess no side-pieces, 

 no transverse furrows, no hydrospire pores, and no sockets for 

 the reception of pinnules; they simply are covered by two rows 

 of Saumplattchen, which enclose a tubular canal containing the 

 food groove. The Saumplattchen or covering pieces of the same 

 row are so closely anch^dosed to one another, longitudinally, that 

 it appears even under an ordinary magnifier, and in the most per- 

 fect specimens, as if there were but two elongate plates, one at each 

 side. As such they were represented bj^ Hall in his diagramatic 

 figure. New York Geol. Rep., vol. ii, PI. 48, fig. 1 1, in which the 

 reniform plates at the outer end of the elongate pieces represent 

 the second radials. The figure shows excellently the plates of 

 the ventral side as they generally appear in the specimens ; there 

 is omitted, however, a suture along the so-called coronal processes, 

 which Hall, as well as Roemer, thought he observed, but which 

 were not accurately defined until 1883, b}" Etheridge and Carpenter 

 (Ann. and Mag. Nat Hist., April, p. 239). They found the pro- 

 cesses " divided into an outer part formed by the contiguous limbs 



