Prof, E. Forbes on Fossil Invertebrata from Southern India. 119 



2. Semi-compressed pipe-like fragments, equal in dimensions throughout, evi- 

 dently closely allied to the Belemnites ? amhiguus of Morton. I have provisionally 

 named them Belemnites ? fibula. The figure (PI. IX. fig. 3) represents the form of 

 the specimen of the natural size. 



Gasteropoda. 



In the following descriptions of the fossil gasteropodous mollusca of Southern 

 India, I have described under each genus all the species of cretaceous age belong- 

 ing to it in the collection, whether from Pondicherry, Trinchinopoly, or Verda- 

 chellum. It will be seen that all the species are new, as might indeed have been 

 expected in this group. The allies of many are to be found among European cre- 

 taceous fossils, but others are, if anything, more nearly allied to tertiary and recent 

 forms. Several belong to genera hitherto considered of very recent creation. The 

 interpretation of these very remarkable peculiarities will be found in the second 

 part of this report. 



The genera are arranged in what I consider the sequence of their alliance. The 

 arrangement differs considerably from that which is usually adopted. I commence 

 with Trochus and its allies (Pleurotomaria ? Nerita and Phasianella), because, 

 among all the genera to be passed in review, these are, in many respects, most 

 highly organized. In them we find indications of a higher organisation, exhibited 

 in the characters of the eyes, tentacula, and appendages of head and body. Natica 

 will be found far removed from its usual but incorrect association with Nerita ; its 

 true position, as is evident to any one who studies and understands the animal, 

 being close to Bulla, where also Tornatella must be placed, its animal being still 

 more similar to that of the last-mentioned genus. 



Genus Trochus, Linnaeus. 



1. Trochus arcotensis, sp. nov. PI. XIII. fig. 9. 



T. testa late conica (umbilicata), anfractibus 5 complanatis, aequaliter (5) striatis, transverse 

 oblique-striatis, ad suturas depressis, ultimo anfractu margine basali acuto, basi plana, concen- 

 trice crenato-striata ; apertura quadrangular!. 



Height Oj\ inch. Breadth Oy^^ inch, 



A conical flat-whorled shell, resembling some varieties of Trochus cinereus in 

 shape. The whorls are five, and are ornamented by a few spiral thread-like ribs 

 with obliquely striated interstices. The striae run over them, and slightly crenu- 

 late the ribs. The base is flat, spirally grooved and ornamented like the upper 

 portion of the basal whorl. There appears to have been an umbilicus, possibly 



r2 



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