402 J. Hall on Cryptonella, Centronella, Meristella, 
be seen projecting backwards between the hands of the loop, as 
well as extending in front, as shown in fig. 
In casts of the ventral valve, we find the marks of two thin 
dental lamelle extending to a greater or less distance below the 
eak, Along the median line in the ventral cast, there is usu- 
ally a narrow ; flattened space limited by a slender line; and on 
each side a less distinct narrow space, limited in the same man- 
ner. In the cast of the dorsal valve, there is a — impresse 
line, and two of less strength on each side 0 
The species of this genus, known to me, are ‘the Cryptonella 
(Centronella) Julia, and those described as Terebratula in the 
rteenth Report on the State Cabinet, and which in the Four- 
teenth Report were referred to Cryptonella, viz. Or yptonella (T.) 
7 eee C. (7) Lens, C.(T.) planirostra ; and C. eximia, of the 
Fy, Report as well as a new species from the Schoharie grit. 
The Terebratula Lincklent, which has the se chara 
with a median swale a and convex at the sides 
The character of the genus, as given in the descriptions and 
3 ene: of Mr. Billings, are as follows 
GEN ENTRONELLA, Billings,’ 1859. — “ Generic Si 
ters : “Shells, having the general form of Zerebratula. Do 
valve with a loop consisting of two delicate ribbon-like lamellx, 
which extend about one-half the length. These lamellx ae first 
curve gently outwards, and then ap- 13. 
proach each other gradually, until at 
their lower extremities they meet at 
an acute angle; then, becoming uni- 
ted, they are reflected backwards to- 
wards the beak in what appears to be 
a thin flat vertical plate. Near their 
origin, each bears upon the ventral 
side a single triangular crural process. ‘ 
Name, from the Greek xevzgor, a spur. 14 (5). Longitudinal section, shor a 
This genus is intermediate between ing the position of the loop ™ 
Terebratula and Waldheimia. In the the interior. a nw, 
former, the loop is short, not exceeding greatly one-thi 
ee of the shell, and not reflected. In the latter, it extends a 
. 18 (4). Interior of tee 
ripti orth os from the Canadian Naturalist and oe 
