24.2 CRETACEOUS GASTROPODA 
LI. BURTINELLA, Morch, 1861. (Vide p. 238). 
1.—BuRTINELLA concAvA, Sowerby, sp., Pl. XVIII, Figs. 11-19. 
1822. Vermicularia concava, Sow., Min. Conch., Vol. I, p. 125, Pl. LVII, Figs. 1-5. 
Burt. testa crassa, discoidea, planorbulari seu subturbinata, late wmbilicata, 
plerumque sinistrorsa, rarissime dextrorsa; apice sepissime detrito; anfractibus 4-5, 
rotundatis, ad suturas nonnunquam callositate tenui instructis, transversaliter striolatis, 
prope aperturam aliquanto cingulis crassioribus nonnullis ornatis, ultimo in adultis 
terminatione ab ceteris dissoluto, ac plus minusve recte prolongato ; apertura circulari, 
marginibus attenuatis. 
The diameter of the coiled shell measures in the largest specimens from 18-20 mm. 
It is impossible to give any specific distinction between our Indian fossil and the 
one described and figured by Sowerby from the Upper Greensand. The shell, being 
composed of three distinct layers and having the apex spirally coiled, presents 
all the characters of a true Gastropod. The form is very variable, generally the 
apex is found corroded, or in some way or other made indistinct, for the shells 
were usually attached when young to submarine objects. Specimens with the 
spiral embryonal whorls preserved are very rarely met with; in a more adult age 
the whorls are spirally coiled either in the form of a disc or of a short cone, being 
generally sinistral, very seldom dextral; they form a large open umbilicus, and are 
either perfectly round or somewhat depressed and joined together with a thin callous 
substance. It is quite impossible to draw a line between the variations of form, 
which can be observed in a large number of specimens from the same locality, and 
which are amply illustrated in our figures. The end of the last whorl is often separated 
from the previous volution and forms a free, more or less prolonged, tube. The 
aperture is circular, or nearly so, and the margins sharpened from within. The 
transverse strise of growth are generally distinctly marked, occasionally in some 
places somewhat stronger, and near the aperture of large specimens producing 
sometimes thick elevated rings. 
Several very similar species have been separated under different names, the 
specific distinctions of which are not always certain. For instance, Sowerby’s Ver- 
micularia wnbonata (M.C., pl. 57, figs. 6-7), seems to be scarcely different from 
the present species. The same is probably the case with Mantell’s Verm. wmbonata 
(1. cit. p. 111, pl. 18, fig. 24), which has been transmitted from Mantell to Sowerby, 
and is from the same locality as the last named. 
Another very similar species is Burtinella Phillipsii, Romer, sp. (Verm. 
Sowerbii in Phill’s. Yorksh., pl. 2, fig. 29), which differs only by its more conical 
shape. In Serpula subrugosa, Mist. (1. cit., pl. 71, fig. 1), the shell appears 
to have been much thinner, and the inner space of the whorls indented by the 
convexity of the preceding whorl, which makes it probable, that it is not different 
from the Burt. (Vermicularia) Sowerbii of Mantell (1. cit., pl. 18, figs. 14-15). 
Localities.—Olapaudy, Andoor and Veraghoor (yellow sandstones) ; Kunnanore 
and Paupanchary, in greyish or yellowish, siliceous sandstones; common. 
Formation.—Arrialoor group. 
