Prof. E. Forbes on Fossil Invertebrata from Southern India. 99 



This species is much-compressed, especially dor- 

 sally : the angles of the mouth project so as to give 

 the aperture a hastate or triangular form. The sur- 

 face of the only specimen is too much worn to be 

 made out clearly. The septa are remarkably si- 

 nuous ; laterally and nearly in the centre they make 

 a bend, the sweep of which is abruptly curved and 

 directed towards the umbilicus so as to form a sort 

 of triangular lobe, resembling in form a porpoise's 

 fin, and angulated at its superior base, whence the line crosses the back in a 

 sHghtly undulated curve. It belongs to a group of forms mostly oolitic. The 

 Nautilus sinuatus of Sowerby and Nautilus hiangulatus of D'Orbigny are its 

 nearest allies. 



Locality, Pondicherry. 



Genus Ammonites, Auctorum. 



There are twenty-three species in the Pondicherry collection. They belong to 

 the following sections, as established by Von Buch and D'Orbigny : — 



1st, Fimbriati, a group especially characteristic of the lowest part of the creta- 

 ceous system and extending into the oolites. To this division belong Ammonites 

 Vishnu and Ammonites Brahma. 



2nd, Ligati, a group of which all the known species are cretaceous, and the 

 greater number from the lowest beds. The Pondicherry species of this division 

 are no fewer than eight, most of them closely allied to fossils of the beds called in 

 France " Lower Neocomian." 



3rd, Heterophylli, a group almost entirely confined to the lowest portion of the 

 cretaceous system. Seven Pondicherry Ammonites belong to this division, many 

 of them extremely near French Neocomian species. 



4th, Flexuosi, a lower cretaceous group of small extent. One Indian fossil, the 

 Ammonites Egertoni, belongs to it. 



5th, Dentati, an extensive group of lower cretaceous forms. Two of the Indian 

 species belong to this division. 



6th, Clypeiformi, lower cretaceous and oolitic. There is one Pondicherry species, 

 Ammonites Siva. 



7th, Armati, a group of upper oolitic forms. Ammonites Menu appears to belong 

 to this section. 



8th, A single Ammonite, A. Rembda, represents a type of forms as yet uncha- 

 racterized, and which I propose to call Lcevigati. 



