No. 1S6.] 101 



TREMATOSPIRA HIRSUTA. 



Atrypa hirsuta : Hall, Tenth Annual Report of the BegentSi p. 128. 



This species, which I referred to the Genus Atrypa on account of its 

 general form and finely plicated surface, proves to belong to the Genus 

 Trematospira; the interior showing spiral appendages, as in the already 

 described species of that genus. This then makes two species of the 

 genus in the Hamilton group. 



The Atrypa uniangulata of Conrad has heretofore remained without 

 the means of determining its structure; but during the present year, 

 1860, I have, through the kindness of Mr. S. S. Lyon, been furnished 

 with the separated valves of a well-preserved individual. The ventral 

 valve bears essentially the character of Meristella; while the cardinal 

 process in the opposite valve is quite peculiar, rising above the level of 

 the hinge-line, and approaching in form the corresponding part of Rhyn- 

 CHOSPIRA, preserving at its base the commencement of the crural pro- 

 cesses. Another specimen shows the presence of internal spires arranged 

 as in Spirifer. These characters ally it with Trematospira, but the 

 structure of the shell is distinctly fibrous ; and in this respect, and in 

 the character of the muscular impression, it is more nearly allied to 

 Meristella; while in the cardinal process, muscular impression, and 

 absence of lamellose structure, it differs from Athyris. 



Should farther examination prove these differences to be of generic 

 importance, it may form a subgenus, for which I suggest the name 



GONIOCCELIA. 



In the preceding Report, I have described as Terebratula, T. linckloeni, 

 T. rectirostra, T. lens, and T. planirostra ; suggesting at the same time 

 that, since the internal structure is unknown, they may prove distinct 

 from that genus. Even before the Report was published, I had satisfied 

 myself that these forms were not true Terebratula. The muscular 

 impressions left upon the shell so nearly resemble those of Renssel^ria, 

 that it might be inferred from the cast that the species belonged to this 

 genus. The exterior form and the extension of the beak give them a 

 different aspect; and the absence of longitudinal or radiating striae is 

 likewise opposed to the known forms of that genus, with one exception. 



These forms begin their existence in the Lower Helderberg group, 

 where I know a single species, while the type becomes farther developed 

 in the Upper Helderberg and Hamilton groups. For these fossils, I pro- 

 pose the name of Cryptonella. 



