ANOMIA. 195 
Awomta pecter. 
“The only specimen in the Linnean collection which at all 
answers to the description is the Strophomene (Orthis) pecten, 
(Dalman, Vet. Ac. Hand. 1827, pl. 1, f. 6.—Hising. Lethea 
Suec. pl. 20, f. 6) still preserved in the box so marked in the 
cabinet. Dalman’s figures and description prove that the Swed- 
ish naturalists have kept up the knowledge of the species. The 
shell to which Sowerby has given the name of Orthis Pecten 
(Sil. Syst. p. 21, f. 9) is very different, and may be readily dis- 
tinguished by its finer and more numerous strie, and by its 
greater length ; O. expansa of Mr. Sowerby (Sil. Syst. pl. 20, 
f. 4) appears to be the cast of the same shell; this latter appel- 
lation may consequently be retained for the Sowerbian pecten. 
“The Linnean species may be described as follows :—Stropho- 
mene pecten. Semicircular; hinge-line straight, slightly pro- 
duced beyond the sides of the shell. Upper valve slightly con- 
vex, flattened near the apex. Under valve nearly flat, raised a 
little towards the apex, and slightly concave at the sides. 
Valves covered with regularly radiating strie, about twenty in 
number at the apex and increasing to near 100 at the margin 
by the insertion of additional striz between the others, and not 
by bifurcation. Striz smooth at the top, roughened at the 
sides by numerous fine cross ridges. One or two strong con- 
centric ridges. Hinge area equal on each valve, sloping inward 
diagonally ; on the upper valve a triangular portion in the 
middle of the area is raised up into an arch forming a semi- 
cone ; in the lower valve is arounded opening opposite to and 
rather larger than the arch. 
“ The specimen being a little chipped at the sides, the produc- 
tion of the ends of the hinge-line can only be judged of by the 
lines of growth on the body of the shell; the breadth of the 
specimen is one inch (if perfect it would probably be an eighth 
more), its length is seven-eighths of an inch. I have found 
this shell in the dark limestone of Coniston, which is the 
lowest bed of the Silurian System in the North of England, 
and I am not aware that it has been noticed elsewhere in this 
country, nor have I found any mention of it in any of the 
