OF SOUTHERN INDIA. 349 
The peculiar expansion of the margins* and the circular aperture must be 
considered as the distinctive characters of this genus, in which only species, like 
Cross. Pratti, Morris and Lycett, or Cross. (Delphinula) reflexilabrum, WOrb., can 
be admitted. The two other species, Cr.? discoideum and Cr.? heliciforme, 
doubtfully placed by Morris and Lycett in this genus, are either not fully grown 
Crossostomata, in which case their specific determination must remain doubtful ; 
or they are full grown shells, in which case they must be transferred to Chrysostoma. 
No cretaceous, tertiary, or recent species of true Crossostoma are as yet known. 
14. Pterocheilos, Moore, 1867 (Quart. Journ. Geol. Soc., Lond., XXIII, p. 549, 
pl. 14, figs. 4-5); (not Pterochilus, Klug, Hooker, Alder and Hancock, and others). 
This genus was lately proposed for a species, Pé. primus, from the liassic conglo- 
merate of Brocastle. The shell is stated to be very thick, small, with the general 
contour angulated or rhomboidal, smooth; spire short, etc.; last whorl centrally 
earinated, the carina terminating in a wing-like boss or projection on the outer lip ; 
aperture with a thick, circular peristome, columella thick, folded, sub-umbilicated, 
greatly extending beyond the peristome, and possessing a wide but shallow sulcus 
towards its base. This genus appears to be related to the species of Crossostoma ; 
it can hardly be classed in any other family. 
The following are the only species of the Umsonp, which have as yet been reported from 
eretaceous rocks, though, as I have already stated, several others of the small, smooth species of 
Trochus, Turbo and Straparolus (or Huomphalus) may be shown to belong to Umbonella, Vitrinelia, 
Mierothyca, and other allied genera, 
1. Rotella Archiaciana, VOrb., 1842 (Pal. frane. terr. crét. t. II, p. 192, pl. 178, figs. 4-6) 
has more the appearance of Photinula, than of a true Umbonium. 
2. Rotella Michoni, Coquand, 1859 (Bull. Soc. Géol. France, t. XVI, p. 956) may be also 
a Photinula, inasmuch as it is marked with spiral and transverse strie. 
3. Rotella cretacea, @Orbigny, 1847, is our Teinostoma id. 
? 4. Pitonellus tuberculatus, Guéranger, 1853 (Essai d’un Report. Pal. de la Sarthe, ete., p. 31). 
M. Guéranger does not mention this species in his recent “ Album pal., ete., 1867,” but he gives 
two figures of the Delphinula tuberculata, Can one of the specimens have been formerly mistaken 
for a Pitonellus ? 
5. Planorbis radiatus, Sow., 1818, Min. Conch. IT, pl. 140, fig. 5, is a true Helicoeryptus, to 
which it has been already referred by d’Orbigny (Prod. II, p. 151). This species was also found 
by Guéranger in the Department de la Sarthe (Album paléont., etc., 1867, pl. 10, fig. 23). 
6. Helicocryptus ornatus, Guéranger, 1855, (Essai Pal. Sarthe, ete., p.31, and Album pal. 1867, 
pl. 10, fig. 22) is very similar in form, but larger and ornamented with spiral striz. 
7. Vitrinella orbiculata, n. sp. ; 
* Similar to the (Platystoma) Suessi, Hornes, from the Alpine Trias. 
