LOWER HELDERBERG ROCKS. 
377 
BEY RIC HI A. 
o 
I have described a species of Beyriciiia on page 317 of the second vo¬ 
lume of the Palaeontology of New-York, without referring to the autho¬ 
rity for the generic name. The species, now constituting a very pretty 
and well-marked group under this name, were confounded with Agnostus, 
till Professor M‘Coy discovered that instead of being a symmetrical 
trilobate crustacean, the lobes or divisions were Unsymmetrical, and that 
the individuals were the separated “ valves of a bivalve entromostracous 
shell ”. 
The following is the description of Professor M‘Coy 1 
Genus Beyrichia (M‘Coy). 
Bcyrichia : M'Coy, Synopsis of the Silurian Fossils of Ireland, p. 57. 
Agnostus and Battus, in part, of authors. 
“ Shell bivalve, rotundo-quadrate : ventral margin slightly concave; 
“ ends very nearly equal, obtusely rounded ; sides equal, very gibbous, 
“ deeply impressed by a strong and wide sulcus, which extends from 
“ the ventral margin nearly to the dorsal, giving a bilobed or reniform 
“ appearance to each valve. Sulcus slightly nearer to the anterior end : 
“ within this sulcus, on each valve and close to the anterior (or smaller) 
“ side, is a lengthened oval tubercle, nearly at right angles with the 
“ ventral margin, and reaching about two-thirds the distance from 
“ thence to the dorsal margin. Surface smooth [or granulose]. 
Beyriciiia granulata ( n. s.)» 
Plate LXXlX B. Fig. 1 a, b, c, d. 
Bight valve semielliptical, the anterior extremity scarcely narrower than 
the posterior : hinge-line straight, a little shorter than the greatest 
length across the middle of the shell. Anterior, posterior and ventral 
[ Paleontology III.] 48 
