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



possible, at present, to determine with certainty the genus of a fossil patelliform 

 shell, or even the family of which it is a member. 

 Locality, Pondicherry. 



Genus Dentalium, Linnaeus. 



1. Dentalium arcotinum, sp. nov. PI. XII. fig. 16. 



D. testa subulata, tereti, subarcuata, Isevi, sub lente striis concentricis minutissimis ornata. 

 Length ly'g inch. Breadth at mouth 0/^ inch. 



A very slightly bent shell, bearing a considerable resemblance to the recent 

 Dentalium entalis, to which indeed it approaches more nearly than to any known 

 secondary forms. The surface when magnified is seen to be marked by very 

 minute concentric striae. 



Locality, Pondicherry. 



2. Dentalium? hamatum, sp. nov. PI. XV. fig. 8. 



D. testa cylindrica, concentrice striata, extremitate posteriori arcuatissima. 

 Length, exclusive of the hook, ly'jj inch. Breadth at the mouth nearly Oy^^ inch. 



This shell, which is shaped singularly like a fish-hook, is possibly not that of a 

 nioUusk, but the calcareous case of an annelide. Yet as all the known species of 

 Ditrupa, the genus of tubicular annelides, with which a Dentalium may be con- 

 founded, have contracted mouths, whilst all living Dentalia have the greatest 

 diameter of the shell at the aperture, I prefer provisionally placing it in the latter 

 genus. 



Locality, Trinchinopoly. It appears to have been gregarious. 



Acephala Palliobranchiata. 

 Genus Terebratula, Bruguiere. 



1. Terebratula arabilis, sp. nov. PI. XVIII. fig. 12. 



T. testa orbiculari, subdepressa, concentrice sulcata, sulcis numerosis, profundiusculis ; mar- 

 gine frontali obsolete bisinuato, foramine magno. 



Length IjV inch. Breadth l/^ inch. Thickness O/g inch. 



A very broad or rather orbicular species, depressed, the ventral valve especially. 

 Both valves are ploughed, as it were, by shallow, regular concentric furrows. The 

 surface is minutely punctate. The frontal margin in full-grown shells becomes 

 slightly bisinuated. The beak of the ventral valves is truncated so as to present a 

 large foramen. In process of growth the shell widens, young specimens being 

 much longer than wide, old ones as broad as long. 



