GASTROPODA. 857 
Carinaropsid@. | 
have an extravagant development of the delicate grano-lineate extension of the 
inner lip which is the principal difference between Protowarthia and Warthia. 
The points brought out in the foregoing paragraph are significant and indicate, 
we believe, that Owenella and Protowarthia, followed by some Tetranota-like type, 
were important stages in the development of Bellerophon. The types named are 
obviously progressive. The first has no slit-band and only a very shallow sinus, the 
second is still without the band but has a broad and deep sinus, while the third and 
fourth have a narrow and very deep parallel-sided sinus or sht which with the 
erowth of the shell causes the formation of a slit-band. 
SracHeLta, Waagen. (Pal. Indica, ser. 13, pt. 2, pp. 182, 171; 1880.) Shells 
agreeing in all respects with Bellerophon excepting that they are smoother and some- 
what unsymmetrically coiled, there being an umbilicus on one side and none, or at 
any rate a shallow one, on the other. Type, S. bifrons Waagen. . 
So far as known no shells of this type have yet been found in A merican deposits. 
Two species occur in the Permo-Carboniferous of India, and five in the Permian of 
the Alps. The latter are described by Stache in his monograph of the fauna of the 
Bellerophon limestone. Regarding the genus, it seems to mark an important 
departure from the ordinary types of the family. We suspect that Stachella may be 
the radical of the ophisthobranchs, but this is a mere suggestion. The Cretaceous 
Bellerophina, @Orbigny, is a similarly unsymmetrical shell, but has no slit-band and 
only a shallow emargination of the outer lip. 
Family CARINAROPSIDA. 
Symmetrical, almost patelliform shells, the aperture being greatly expanded; 
apex small, involute, overhanging the posterior margin, consisting of no more than 
two volutions. Within the aperture a broad concave septum. Anterior lip with a 
central emargination. 
This family embraces a small group of Lower Silurian shells that is readily dis- 
tinguished from other bellerophontids by the internal septum. We believe that it 
should include also the genus Pterotheca, which is now almost universally referred 
to the Pteropoda. A discussion of the affinities of this genus will be found under 
Carinaropsis. . . 
Carrnaropsis, Hall.* (Phragmostoma, Hall,+ not Waagen.{) Shell consisting of 
little more than two volutions, the inner one very small, scarcely embraced by the 
outer, and shown in the umbilicus; outer volution greatly expanded, the whole shell 
appearing somewhat patelliform; dorsum carinate, the carina sharp on the inner 
 * Paleontology of New York, vol. i, p. 183; 1847. 
+ Fourteenth Rep. N. Y. St. Mus. Nat. Hist., p. 94; 1861. 
+ Palzontologica Indica, ser. 13, pt. 2, p. 131; 1880. 
