ADDENDA. 
421 
Uliyncliospira subglobosa. 
PLATE LXIII, FIGS. 28-25. 
Among the -collections from the Schoharie grit, there are a few specimens 
of Rhynchospira which have much the general appearance of R. globosa of 
the Lower Helderberg group. They differ in having a smaller number of 
stronger plications, with a single, more prominent one in the middle of the 
dorsal valve, and a corresponding wider depression on the ventral valve; 
while in R. globosa there are one, two or three smaller plications forming 
a kind of mesial sinus on one or both valves, which is a constant and 
characteristic feature of the species, as also of all those of the Genus in the 
Niagara and Lower Helderberg groups. 
This simple mesial plication, together with the globose form, will distin¬ 
guish this from any described species of the Genus. 
Remarks upon the Character of the Crura and Loop of Terebrattjla and 
Cryptonella illustrated in this volume. 
A careful examination of the interior structure of the Terebratuloid 
shells, has shown sufficient ground for the separation of the Genus Crypto¬ 
nella, and the external character of the shells would seem to afford the 
necessary means of distinguishing the Genera. Among the species included 
under the Genera Terebrattjla and Cryptonella, there are three distinct 
forms of loop which are in some degree connected with an external differ¬ 
ence in the form of the shell. 
The simplest form of loop observed is similar to that of Terebrattjla 
proper, but with the anterior extension of the crura free, or not connected 
by any visible extension of the calcified substance of the loop, the extremities 
appearing as if broken. There may have been some connexion of the parts 
by ligament or otherwise during the life of the animal. This form of loop, so 
[Paleontology IV.] 55 
