OF SOUTHERN INDIA. 365 
17. Cardinalia, Gray, 1847 (ibid. p. 413), has the inner lip simply curved, not 
twisted posteriorly, thick, smooth, and in front terminating abruptly. 
18. Tectus, Montf., 1810 (bid. p. 413 ;—Pyramis, apud Gray and Philippi; 
Pyramidea, Swains.). Montfort appears to have figured the Zroch. Mauritianus. 
Gmel., as the type of this genus, as this is the only species which occasionally 
has two rather strong fold-like teeth on the outer lip. The inner lip is in this 
genus anteriorly twisted and distinctly thickened, which is the only traceable dis- 
tinction from Trochus, but it appears to be constant. 
19. Polydonta, Schumacher, 1817 (ibid. p. 414); the margins of the aperture 
are in this genus generally somewhat thickened, the inner lip posteriorly twisted, 
then almost straight, toothed or tuberculated at the edge ; the axial cavity is usually 
furnished with a few callous ridges. 
20. Ziziphinus, Leach, 1840 (ibid. p. 421—Caliostoma, Swains., ex parte). 
Shell conical, whorls generally flattened or slightly convex, inner lip thickened, 
gently curved, smooth, anteriorly terminating obtusely and mostly covering the 
umbilical region. 
21. Hutrochus, Adams, 1863 (Proc. Zool. Soc., London, p. 506), has been 
proposed for a Ziziphinus-like shell, Hut. perspectivus, being remarkably thin and 
having a perspective umbilicus. Should this group include also the umbilicated 
Ziziphini which have a thicker shell ? 
Of all these six last named genera the species of Ziziphinus are most numerous 
in the present seas, and the same appears to be the case with the fossil ones. It is 
probably not an over-estimate to say that at least one-tenth of all the known species 
of Zrochus from jurassic and cretaceous deposits belong to Ziziphinus. A great 
difficulty exists, however, in the correct determination of the genera, because the 
inner lip is, in the fossil species, very often not so perfectly preserved, or so 
thoroughly exposed as could be desired, and we must therefore in a great many cases 
make our determination solely dependent upon the general form of the shell. 
The cretaceous species can be partially referred to Zectus, partially to Ziziphinus, imperfect 
specimens of both not being distinguishable from Zrochus, and the same must be said with regard 
_ to Hutrochus as compared with the umbilicated species of Ziziphinus. Forms directly answering 
to the characters of Polydonta and Carinidea are not known from cretaceous deposits, although 
the Pleurot. Scarpasensis, d’Arch., has a great affinity to the last genus. 
Species apparently belonging to Tectus are Trochus Guerangeri, WOrb., Tr. Couveti, Pict. 
et Renev., Zr. Reneviert, Pict. et Camp. and others. I shall notice two new species from our 
South Indian cretaceous rocks, Tectus tamulicus and junceus, the former unquestionably belong- 
ing to this genus and the latter with the greatest probability. As characteristic species of Ziziphinus 
I may mention Zroch. striatulus, Desh., Tr. girondinus, d’Orb., Tr. Cordieri, Buneli, Huoti, and 
Rozeti of d’Archiac (probably representing only one or two species); Zr. Pertyi, Fischeri, Morteau- 
ensis, Laharpi, Gaudini, Buvigniert, Gessneri, Gillieroni of Pictet and Campiche and others, 
described by Coquand, Reuss, Geinitz, Binkhorst and Guéranger (see Mat. p. 1. Pal. Suisse, 3me. 
ser.). As more properly belonging to Zrochus, on account of a conspicuous depression in the centre 
of the basis, I may quote Zr. Zollikoferi, Chavannesi, Oosteri of Pict. and Camp., Zr. Razou- 
mowski, Pict. et Ren., Zr. Marrotinus, d’Orb. and others. From our cretaceous deposits I have 
to mention only one well known European species, Ziziphinus Geinitzianus, Rss., which generally 
has a narrow umbilicus, and thus is allied to the form designated by A. Adams Eutrochus. 
4W 
