Prof. E. Forbes on Fossil Invertebrata from Southern India. 161 



twelve or thirteen pairs. The postero-lateral depressions are deepest. The anal 

 truncation is nearly perpendicular. Beneath, the cheeks are very flat or almost 

 concave, and the post-oral space is slightly convex and broadly ovate. 



3. Brissus Rana, sp. nov. PI. XIX. fig. 5. 



B. ambitu suborbiculari, subangulato, dorso elevato, vertice subcentrali (postico) ; ambu- 

 lacris profunde impressis, antero-lateralibus longioribus lanceolatis, posticis ovatis, sulco antico 

 profundoj lato, lateribus subdeclivis, inferne spatio post-orali late ovato. 



Length 1^ inch. Breadth ly^^ inch. Greatest height 1/^ inch. 



A very tumid, subglobose species, slightly broader than long and rather angular 

 in outline. The sides slope steeply. The anal extremity is suddenly and perpen- 

 dicularly truncate. The anterior and central furrow is rather wide, and has sides 

 which appear to slope, owing to the rounding of their angles. This furrow is not 

 so deep as the latero-dorsal ambulacra. The anterior pair are lanceolate, and the 

 posterior ovate, approximate and very deep. In the former are twenty-three pairs 

 of pores in each series, placed on the slopes of the depression ; in the latter 

 eighteen. Beneath, the surface is convex posteriorly in consequence of the form 

 of the post-oral space, but the cheeks are nearly flat. 



The nearest allies of this species are tertiary. The chalk " Spatangus Bucar- 

 dium" of Goldfuss also comes near it. 



Genus Nucleolites, Lamarck. 



Under this generic term I would include all the Chjpeasterida with petaloid 

 interrupted ambulacra and a supra-marginal anus. The genera Clypeus, Nucleolites, 

 Cassidulus, Catopygus, and Pygorhynchus, are so many sections, not always very 

 definite, of the genus so constituted. The following table will show their relations 

 at a glance : — 



Mouth with tuber- 

 cles = Clypeus (Klein), Agassiz. 



Mouth without tu- 



A. 

 j Anal furrow .strongly 



Anus placed high up. < 



r Nucleolites, as restricted by 

 bercles 



Anus placed far back. 



I marked i ., , ., , I Agassiz. 



' Mouth with tuber- ° 



cles ^ Pygorhynchus, Agassiz. 



Mouth without tu- 

 bercles ...... = Catopygus, Agassiz. 



B. 

 Anal furrow obsolete (Mouth with tubercles) = Cassidulus, Lamarck. 



1. Nucleolites {Pygorhynchus) testudo, sp. nov. PI. XIX. fig. 2. a, h. 



N. ovatus, gibbosus, vertice supra-anali, marginibus declivis, sulco anali lanceolate, declivi. 

 Length Ij*^ inch. Breadth ly\j inch. Heig.it 0/^ inch. 



