THE NAUTILUS. Sh 
The writer’s first knowledge of the characters of the two species 
certainly convinced him that they were widely separated, and in 
order that this fact might be made apparent to others, some fine 
suites of both forms were shown and commented upon at a recent 
meeting of the Phila. Acad. of Nat. Sciences, and, it may be added, 
that the conchologists present fully endorsed the views of the speaker. 
The several prominent characters exhibited by C. fornicata are as 
follows : 
Ist, the dateral curve of the apex, which, though very prominent, 
is, as a rule, closely attached to the body of the shell. ; 
2d, the bow-like curve of the free edge of the interior arch. 
3d, the well-defined nick at the junction of the latter with the 
outer wall of the shell. 4th, the concave form of the septum, which is 
the same in all stages of growth. 
Other characters might be noted, but those given will doubtless 
suffice to separate the species, as C. glauca has none of the features 
alluded to. 
The apex of the latter species is quite small and comparatively 
free from contact with the body of the shell. — It is also horn-like in 
appearance, usually shining, and but slightly inclined to curve 
laterally. 
The free edge of the septum is straighter than that of C. fornicata, 
and the notch is not only absent but replaced by a slight advance 
of that part of the plate along and against the inner wall of the 
shell. Another, and perhaps the strongest character of the group is 
the convex form of the septum. 
This feature, which is a constant one, may be safely depended on 
to distinguish the species at once trom C, fornicata in which the septum 
is always depressed. The general outline of the shells will also help 
the student to divide the species, C. fornicata as a rule being pear- 
shaped, while C. glauca is usually disk or quoit-like in form. The 
prevailing color of the latter is also a distinguishing mark, the inside 
of the shells being ofa dark brown color and the outside a dark gray 
or purple. 
That a species so well marked as C. glauca should be dropped or 
mergéd into another without a given reason, is no small matter, and 
more than one, student will doubtless thank the eminent Doctor for 
some explanation. 
It may be of interest for some readers of the “ Nautilus” to know 
that a very fine suite of the shells can be seen in the New Jersey 
