FOSSILS OF THE NIAGARA GROUP. 359 



GENUS HEMICOSMITES, Von Buck. 



This genus was established by Von Buoh for a fossil figured by Pander, 

 under the name of EcMnosphcerites malum. 



The body consists of four series of plates ; the basal series containing 

 four plates, of which two are hexagonal and broad, and two narrower 

 ,and pentagonal, similar to those of Cartocrinus. The second or 

 subradial series consists of six plates, which are likewise very 

 similar to those of Cartocrinus, except that three, instead of two, 

 are truncated at their upper margins ; and two of them are exca- 

 vated on their upper adjacent lateral angles for the ovarian aperture 

 which lies between these and the base of one of the plates of the 

 succeeding range. In the third range of plates this genus differs 

 from Cartocrinds in having nine instead of eight plates ; the ninth 

 comes in by a truncation of a plate of the second range, which 

 corresponds to the plate directly opposite the ovarian aperture of 

 the other genus. The mouth is represented by Von Buch as central. 

 It is not known to possess arms or tentacula. 



Among the fossils of the Niagara group in New York are some sepa- 

 rated plates which I have supposed may belong to this genus ; but their 

 relations have not been fully established ; though I have little doubt that 

 further examinations in some of the more prolific localities will show the 

 occurrence of this genus. 



Among the cystideans of the same group in Wisconsin there are several 

 specimens which preserve the structure and general features of this genus ; 

 but they are for the most part obscure. 



Hemicosmites subglobosus, n. s. 



PLATE XII, FIG. 13. 



General form subglobose, a little longer than wide, somewhat narrower 

 above than below ; the ovarian aperture above the middle of the 

 length; scarcely produced at the base, which is sometimes sub- 

 truncate or even a little depressed. [This latter feature is probably 

 due to accident.] In the lower range the plates are short, and the 

 second range consists of comparatively wide plates, giving it a greater 

 proportional width than the typical species of the genus. The mouth 

 is at the summit, but it cannot be determined whether it is or is not 



