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



chalk of Maestricht and equivalent formations*. That species, however, has the 

 apex of the back in the region of the ocelli. The Indian species has a narrower 

 anterior groove. It is also allied to the Holaster V Hardy of the Neuchatel green- 

 sand, but differs in the disposition of the ambulacra. 



Genus Brissus, Klein. 

 (Including Micraster, Schizaster, and Brissopsis of Agassiz.) 

 1. Brissus expansus, sp. nov. PI. XIX. fig. 7. 



B. ambitu suborbiculari ; dorso depresso, vertice centrali ; ambulacris impressis, antero- 

 lateralibus longioribus, posticis lanceolatis, sulco antico profundo, lateribus abruptis, parallelis ; 

 inferne spatio post-orali late ovato. 



Length 2/^ inches. Breadth 2/^ inches. Greatest height Ij^^ inch. 



Nearly round, or very broadly cordate, depressed but convex. The dorsal ambu- 

 lacra are all petaloid and narrow, the antero-laterals being to the posterior ones 

 as three to two. The former have about thirty-two pairs of pores, connected by 

 grooves, in each series ; the latter about twenty-three. The ambulacral impres- 

 sions are flat centrally, and the lowermost pore of each pair is advanced a little 

 towards the centre of the plane. The junction of the ambulacral plates in the 

 centre of the depressions appears as a fine undulated ridge. The anterior central 

 ambulacral groove is rather narrow and has very steep parallel sides. The anal 

 end is very obtuse and the truncation slopes rapidly tow^ards the under-surface. 

 The post-oral space is broadly ovate and rather convex, but the cheeks are nearly 

 flat. 



This Brissus is allied to a common miocene form from Malta. 



2. Brissus incequalis, sp. nov. PI. XIX. fig. 6. 



B. ambitu orbiculari-cordato, dorso depresso, vertice subcentrali ; ambulacris leviter im- 

 pressis, antero-lateralibus multo longioribus, posticis ovatis, sulco antico lateribus divergen- 

 tibus ; inferne spatio post-orali late ovato. 



Length l^-^j inch. Breadth ly^^ inch. Greatest height 0/^ inch. 



Orbicularly cordate, depressed, but more convex than the last species, to which 

 it is very nearly allied. The sides are more sloping. The frontal furrow is deep, 

 and gradually widens. The antero-lateral ambulacra are very long, and have nearly 

 parallel sides through the greater part of their length. The postero-lateral ones 

 are very short and ovate. The former have twenty-five pairs of pores connected 

 by grooves, placed on the slope of the depression in each series. The latter only 



* It is said to occur in greensand at Lyme Regis in England. 



