PAL3B0NT0L0GICAL REPORT OF GEOLOGICAL SURVEY. 



475 



Its proportions are as follows : 



Heighth, - • 



Greatest breadth across the lobe pieces, ' - 

 Greatest breadth at the top of calyx — narrow 



side, 



Greatest breadth at the top of calyx — wide 



side, 



Heighth of calyx, - 

 Heighth of radials, - \ - 

 Heighth of basal pieces, - 



Long diameter of basal pieces, - 

 Short diameter of basal pieces, - 



The genus Asterocrinus, by its lobed basal pieces, is allied to Dicho- 

 cririus, also by the number of its primary r.idials Here the analogy 

 ceases. Dichocrinus partakes much of the character of the Platycri- 

 nites. The primary radials are generally longer, and the calyx high ; 

 the radials of all known species of Dichocrinus are higher than the 

 basal pieces, while in Asterocritius the breadth of the radials are equal 

 to twice their hight. In the remarkable lobe pieces it is distinguished 

 and separated from all known genera. It is evident the species under 

 consideration had no vaulted covering to the stomach, as the lobe pieces 

 rise from the basal pieces, (to which they are attached,) and nearly 

 fill the cavity of the body. The lobe pieces are free, except at the 

 point of attachment at the base, were expansile, and are indeed'aux- 

 iliaries of the arms, probably serving in part to sieze and crush its food. 

 Fixed to the base by a muscular ligament, articulating by joints, they 

 were evidently capable of opening with, or even independently of the 

 arms. Our specimen is closed ; the arms are folded between the lobe 

 pieces. Six half sets of the arms have their entire length, and are 

 folded toward the centre of the summit, which they do not reach, leav- 

 ing the junctures of the lobe pieces exposed. 



In a paper read before the Academy of Sciences, at St. Louis, Mis- 

 souri, in 1857, our specimen is referred to, and classed with Dichocri- 

 nus; vie differ from the author of tbat paper, and hold that our species 

 is essentially different, and should be separated from Dichocrinus. 



