NIAGARA GROUP* 
267 
This species is evidently closely allied to D. elevata of Dalman ; but the apex is not 
incurved, and in two specimens examined the foramen is narrow and linear, and filled by a 
projecting callosity, unlike the representations in Dalman’s figures. It is possible that a com¬ 
parison of specimens, which I have had no opportunity of making, will show a more close 
alliance than appears from the figure. 
This is an extremely rare species, two only having been seen. It is allied in form to a species 
in the shaly limestone of the Helderberg, and to another in the Hamilton group, but is distinct 
from either. 
Fig. 7 a. The ventral valve of this species. 
Fig. 7 b. Dorsal valve of the same. 
Fig. 7 c. Cardinal view, showing the area and long linear foramen which is closed. 
Fig. 7 d. Profile view of the same. 
Fig. 7 e. Several of the plications enlarged, showing the concentric striae. 
Position and locality. The only two specimens seen were collected- in 1837, from near the 
top and just below the edge of the cliff on the Niagara river above Lewiston. It has not been 
seen in any other locality, and is doubtless a very rare species. 
NOTE. 
TEREBRATULA, ATRYPA, HYPOTHYRIS, &c. 
In the present state of our knowledge, and in the divided or unsettled opinion of authors upon 
this subject, I have preferred to allow the fossils of this family of the Brachiopoda to remain 
under the Genus Atrypa, to which, strictly, many of them do not belong. I am averse to using 
the name Terebratula indiscriminately, according to most of the European continental authors : 
neither does it appear well established that all the subdivisions proposed are tenable, or founded 
upon structural characters of sufficient importance. That the whole group requires a reorganiza¬ 
tion, is but too apparent; but we have, in attempting to introduce Delthyris, Strophomena, 
and other genera of Brachiopoda, occasioned, to beginners, more confusion and uncertainty than 
advantage. These reasons, therefore, must be my apology for leaving, for the present, these 
species under the Genus Atrypa. 
