124 PROCEEDINGS OF THE ACADEMY OF [1886. 



describes it as a Cystid, Carpenter was more inclined to place it 

 with the Blastoids ; while we take it to be a Palseocrinoid of low 

 organization. 



There arie several points in Wetherby's description with which 

 we cannot agree. He describes the mouth or ambulacral orifice 

 as situated nearly centrally upon the upper surface. We had 

 several of Wetherby's best specimens for comparison, but were 

 unable to observe in any of them an external oral orifice, and 

 doubt if such an orifice existed in this Lower Silurian genus 

 " upon the surface." Neither can it be ascertained from tiie 

 specimens whether there were proximals surrounding the oral 

 plate. Wetherby further speaks of " a valvular anal opening, 

 placed between the upper azj^gous plate and the mouth," and he 

 mentions " a proboscis or ventral sac " which was said to be 

 " indicated by the presence of the upper azygous plate." If it is 

 meant that the so-called " valvular opening " is separated from 

 the ventral sac, and we infer it from fig. 1 on Plate 5, which shows 

 an irregular break upon the ventral surface in the direction to 

 which he alludes, he is certainly in error. Even if an opening 

 did exist, we doubt if he could have observed small, valvular 

 pieces in specimens in which even the larger ventral plates cannot 

 be distinguished. If he means that the anal opening is connected 

 with the ventral sac, placed along its inner or ventral side, we 

 can partly agree with him. 



Wetherby described the genus as having in three of its rays 

 arms like those of the Crinoidea, in the other two raj^s appressed 

 ambulacra, such as occur in the Cystidea. He does not say any- 

 thing about the length of the three arms, leaving it in doubt, 

 whether he took the three projections to be only the stumps of 

 the arms, or as representing their full length. He only mentions 

 that the arms are composed of a single row of plates, that they 

 are very deeply excavated at the inner side by the ambulacral 

 furrows, and that the latter are covered by a closel}^ interlocking 

 series of small plates, having the same arrangement as those of 

 the two appressed ambulacra. He mentions further a more or 

 less obscure furrow upon the outer surface, " of which nothing 

 further is known." 



Carpenter, in his paper on Hybocrinus and Hyhocystites^ called 

 attention to the fact, that in Wetherby's figures, and in the speci- 

 mens which he had examined himself, only one or two so-called 



