OF SOUTHERN INDIA. 391 
1. Scuwtus, Montf., 1810; shell rather thick, depressed, very oval; apex 
posteriorly pointed, slightly incurved ; outer surface with concentric strise of growth, 
and occasionally with some lateral, thin radiating ribs ; aperture anteriorly truncate 
or emarginated, the emargination being externally on the shell traceable by the 
indentation of the strie of growth. 
There are a few tertiary species of Scwtws known (Se. Bellardi, Mich.), but 
I do not think that any of those described by Deshayes from the Paris basin under 
the generic name Parmophorus belong to this genus. Pictet and Hérnes have 
already remarked, that the shell of those species, noticed by Deshayes, is very thin, 
and is neither truncate nor emarginated in front. Comparing the last figures (in 
Deshayes’ Anim. s. vert., 2nd edit., vol. IT, pl. 8), it will be seen that the horse-shoe 
shaped, muscular impression of the Paris specimens does not agree with the 
impression of the shell of Scutws, in the living specimens of which such an 
impression does not at all exist, the adductor muscle being entirely attached to the 
top of the shell, from near the margin to the apex. I believe that all the species 
of Deshayes’ Parmophorus belong to Nacella or Patina, a genus of the 
TECTURIDE. 
La. Tugalia, Gray, 1853 (Tugali apud H, and A. Adams, Gen. I, p. 455) 
only differs from Sewéws in having the upper surface cancellated, and the margin 
of the aperture crenulated and deeply insinuated in front. 
_ 2. Emarginula, Lamarck, 1801. Shell cup-shaped, with the apex incurved, 
spiral, posterior, aperture in front with a median slit. 
2a. Sub-emarginula, Blainville, 1825, has the shell usually somewhat 
irregularly oval, the surface covered with unequal, often tubercular ribs, and the 
anterior emargination very short. The latter is occasionally somewhat lateral, 
as in the cretaceous Hm. neocomiensis, D’Orb., or in Emarg. impressa and galericu- 
lus of Ryckholt, though these fossil species have the slit much deeper than any 
recent Subemarginule, and will probably have to form a distinct subgenus. The 
devonian Hmarg. conoidea, Goldf., belongs to the Capuzipz. 
2b. Clypidina, Gray, 1847, has the surface cancellated or spinose, aperture 
with a single groove in front on the right side, extending to the apex and resem- 
bling that of Stphonaria. 
Gray also places Deridobranchus, Ehrb., in this family, stating that the animal 
is like that of Emarginula, without any shell; the front of the mantle being 
plaited and covering the pectinate gills. Upper tentacles are said to be none, lower 
“two” and the “‘ eyes at the base of the lower tentacles.” I cannot make out the 
meaning of wpper and lower tentacles, but in the Op. NuDIBRANCHIATA there are 
occasionally somewhat similarly formed Molluscs to be met with, in which various 
appendices on and above the head can be mistaken for tentacles. 
3. Zeidora, Adams, 1860 (Ann. mag. nat. hist., V, p. 301), has a shell like 
Emarginula, with the margin of the aperture crenulated and anteriorly deeply 
fissured, but there is posteriorly an internal, flat, semilunar septum present, which 
distinguishes this genus from any other FrssvrzELzip2z. 
