Mr. R. Etheridge on Carboniferous Lamellibranchiata. 431 
Genus Scuizopus, King, 1844, 
Annals Nat. Hist. 1844, xiv. p. 315; Permian Fossils, 1850, p. 185. 
Schizodus Saltert, sp. nov. 
Schizodus, sp. (Salter), Rev. T. Brown, Trans. Roy. Soc. Edinb. 1861, 
Xxli. p. 392, figs. 1-3. 
Spec. char. Very inequilateral, convex and prominent in 
the umbonal region; anterior side rounded; posterior side 
longer and more compressed than the anterior, slightly trun- 
cated obliquely, narrowed by the convergence of the dorsal 
and ventral margins; ventral margin gently rounded; an 
obtusely rounded and curved diagonal ridge proceeds from the 
beak of each valve to the postero-ventral margin, enclosing 
between it and the dorsal margin a narrow, slightly concave, 
posterior slope. Beaks pronounced, prominent, slightly in- 
curved towards the anterior side; valves very prominent and 
convex in the umbonal region, rapidly arching downwards to 
the rounded ventral margin, In the right valve the anterior 
tooth is inclined a little obliquely towards the anterior side ; 
the posterior tooth is elongated. In the left valve the large 
central tooth is very prominent, thick, plain, and projects 
somewhat outwards from the umbonal cavity ; although not 
bifid, the ventral margin of this tooth appears in some speci- 
mens to be very slightly concave, thereby indicating a ten- 
dency towards the bifid form; anterior and posterior teeth 
obscure. The scar of the anterior adductor is oval, and 
attenuated towards its dorsal extremity; the posterior im- 
pression also oval, but rather larger than the anterior. Pallial 
line well defined on the anterior and posterior sides, less so in 
the middle of its course; an internal curved ridge extends 
from the umbonal cavity on the posterior side obliquely 
towards the postero-ventral mar gin, and nearly corresponds in 
position with the diagonal ridge. Surface of the shell towards 
the ventral margin is marked by several well-defined laminz 
of growth, between which and over the general surface are 
close fine strie, usually only faintly preserved. 
Obs. In connexion with this shell, the Rev. T. Brown 
makes the following remarks in his paper on the “ Mountain 
Limestone and Lower Carboniferous Rocks of the Fifeshire 
Coast, &c.””* :—“ Dr. Fleming, to whom I formerly submitted 
this shell, considered it to be the Anatina attenuata of M‘Coy 
but held that it had been erroneously referred to that genus. 
He possessed numerous specimens from a bed near Colinton, 
where it occurs in such abundance as to suggest the idea of its 
* Trans. Roy. Soc. Edinb. xxii. p. 395. 
