Foerste.] 
310 
[May 1 
to place Orthis fasciata under Orthis calligramma , I suggest that 
their relationship needs further investigation. 
Two forms of Orthis calligramma are found at Colinsville, Ala- 
bama. The first is more typical of the species than are the New York 
representatives. Specimens are often 25 mm. long and 30 mm. 
broad. The ventral valve is decidedty convex, not flattened ante- 
riorly, and the muscular scars are like those of variety virgata , 
Salter, excepting that the low mesial elevation, separating the same, 
is not produced anteriorly. The dorsal valve is convex, the convex- 
ity not equalling that of the ventral valve. The muscular scars are 
not strongly defined anteriorly, but are separated by a low mesial 
elevation, and posteriorly form a concave curve. The radiating 
striae are coarse and distant, in the internal cast, more frequent 
and less distant on the exterior frequently. 
The second form found at Collinsville, Alabama, has a moderately 
convex ventral valve, more or less flattened anteriorly. The mus- 
cular impressions are the same as those of the first form, or are 
somewhat more triangular or rather rhomboidal. The dorsal valve 
is moderately convex. The muscular scars anteriorly are well de- 
fined, and separated by a mesial elevation, which is also quite prom- 
inent anteriorly. The muscular scars approach nearer to the beak 
than in the first form. The cardinal line not infrequently exceeds 
the width of the shell slightly. The plications are usually much 
more numerous in this form than in the first, and there is less dis- 
parity between the number of striae suggested by internal and ex- 
terior casts. The increase in striae is mainly effected by rapid 
intercalation towards the anterior margins. 
In the possession of flattened ventral valves and angular pos- 
tero-lateral margins, the second form approaches the New York 
specimens, but differs from the same in the more numerous striae 
and the occasional extended hinge line, thus apparently forming a 
passage to Orthis fasciata, Hall. In the character of the muscular- 
scars of the dorsal valve the form approaches Orthis jlabellulum, 
and the flattening of the ventral valve tends the same way. The 
character of the muscular scars of the ventral valve is totally un- 
like that of Orthis Jlabellulum, but entirely like well known forms of 
Orthis calligramma , to which it is referred. As will be seen by the 
foregoing, the different characters are combined in different ways 
so that the only means of distinguishing Orthis Jlabellulum from 
Orthis calligramma are the character of the muscular scars in the 
