OF SOUTHERN INDIA. 419 
at the suture with a distinct impressed line. The shell is smooth, rather elongated 
and anteriorly somewhat attenuated, being by these characters easily distinguished 
from the next species, with which it has been previously confounded. 
Locality —Comarapolliam, in softish, rather coarse sandstone with siliceous 
grains ; rare. 
Formation.—Arrialoor group. 
3.. TROCHACTHON CYLINDRACEUS, Stoliczka, Pl. XIV, Figs. 10-14. 
Trochact. testa ovato-elongata, cylindracea, levigata, antice atque postice paulo 
attenuata, spira plus minusve prominente, obtusiuscula ; anfractibus angustis, postice 
oblique et anguste applanatis, deinde subcarinatis ; striis incrementi in superficie 
ultimt anfractus lente curvatis, apertura longa, postice angustissima, antice latiore 
ac rotundata ; labro ad marginem acutiusculo, levigato, antice oblique late ac lentis- 
sime effuso; labio levissimo, postice paulo incrassato, antice triplicato: plica antica 
tenuissima, postica crassissima. 
Spiral angle 75°- 90°. 
Height of spire : total of shell (considered as 1:00) ... Ay eo 0:25 - 036. 
Width of last whorl : height of shell (considered as 1:00)... ww» 0°44-0°55. 
This species is closely allied to several European forms, like some varieties of 
Trochact. giganteus and especially the Trochact. Lamarckii, Sow. sp.; but among 
several hundreds of specimens which we possess, and which were obtained from 
various distant localities, I find that the cylindrical, anteriorly and_ posteriorly 
almost equally obtusely attenuated form of the shell appears to be a characteristic 
distinction, while in all the other species the whorls are ese perceptibly more 
tumid thin they are anteriorly. 
The slightly curved fine strive of growth can be generally clearly traced on 
the last volution. The aperture is anteriorly very slightly effuse, and the inner 
lips thickened and anteriorly provided with three oblique folds, of which the posterior 
one is the strongest. 
Worn specimens are often found in two very different conditions; either only 
the posterior edge of the whorls has been corroded, and in such case the spire 
appears much more raised, than is usual in well preserved shells; when, however, 
the upper corrosion has far advanced the spire becomes very much shortened, and 
thus the appearance of the shell is considerably altered. 
Perfect specimens even of small size are always of a distinct cylindrical shape, 
but those specimens which represent internal parts or fragments of larger ones 
appear sometimes considerably attenuated in front (see Pl. XIV, Fig. 10). This is, 
I believe, produced by the anterior portion of the shell being more absorbed or 
dissolved away, than the posterior; it is on this account that the anterior folds 
are often difficultly traceable in such fragmentary specimens; in fact fragments 
may be found in which the two anterior folds have almost entirely disappeared.* 
* See previous notes on the genus Trochacteon. 
