182 CRETACEOUS GASTROPODA 
of the ZHuziuzpm with the Pyrrammerztripz, and our separation may be justly 
considered a forcible one. There is some drawback to every attempt at classifi- 
cation; nothing will fit properly in the frame we try to make for nature! 
Several propositions have been previously made as to the division of the 
Nerinee into several genera, but we are certain that none based upon a single 
character, like that of Sharpe on the number of folds, can be successful. We do 
not pretend that we have obtained success with our present proposition, but we 
trust it will be found a step further on towards the solution of the problem. We 
believe that only a division, which is based upon the total form of the shell, but 
which must at the same time pay strict attention to all the other characters, as, 
for instance, the number and position of folds, length of the anterior canal, 
ornamentation, etc., can finally succeed. 
XLITT. ODOSTOMIA, Fleming, 1848. 
(Vide p. 173.) 
1.—Opostom1A ANTIQUA, Stoliczka, Pl. XXI, Fig. 6. 
Odost. testa conica, solidula, spira acuminata; anfractibus 5—6, levigatis 
atque politis, convexiusculis, regulariter crescentibus ; ultimo subinflato, ad periphe- 
viam rotundato; basi in adultis specimimibus spiraliter sulcata; apertura ovata, plica 
columellari sub-antica, oblique torta. 
Spiral angle 45°—50°; sutural angle 6°—8°. 
The slightly convex and regularly increasing volutions appear to be specially 
characteristic for this cretaceous form. Young specimens are perfectly smooth ; 
more fully grown have the basis of the last whorl spirally suleated. The number of 
whorls of the species is somewhat larger than in many other Odostomie and may 
be said to form a transition to Syrnola, which is, however, still more elongated and 
more like Obeliscus. 
Locality —Garudamungalum, in a blueish caleareous sandstone ; rare. 
Formation.—Trichinopoly group. 
XLIV. ITRUVIA, Séoliczka, 1867. 
(Vide page 177.) 
1.—Irruvia GLoBorpEs, Stoliczka, Pl. XIV, Fig. 1. 
Tt. testa ovato conica, levigata, spira brevi ; anfractibus gradatis ; ultimo maxiuno, 
subcylindrico ; apertura ovali, postice angustata ; columella antice uniplicata. 
Spiral angle 78°—82°. 
A smooth, ovate shell, with a short spire composed of numerous volutions, 
which terminate abruptly at the suture. The last whorl is subcylindrical, with 
slightly convex outer periphery, more than twice as high as the Spire, and 
anteriorly abruptly contracted. The aperture is ovate, posteriorly narrower, and 
anteriorly with one columellar fold. 
