318 CEETACEOUS PELECYPODA 



12-16, lamelliformibus, actttis, distantihtis, in declivitate postica continuis inter- 

 spatiis latis, hcmd profundis, mimttissime striatis, notata. 



This interesting small form may be regarded as a miniature of the European 

 T, excentrica, Park. The ribs on the surface are peculiar, sharp, but little pro- 

 minent, and with very shallow, broad, minutely striated interspaces. The lunula 

 and area are both distinctly margined, narrow, and smooth, the first somewhat 

 excavated, the second almost quite flat. It is very rare that a distinct lunula is 

 present in any of the species of Trigonia, only the '' GlahrcB' have it occasionally 

 indicated, though I do not know a single species which has it equally marked as 

 this small Indian shell. It might, therefore, be suggested that the species could 

 rather belong to Astarte than to Trigonia ; but against this the examination of the 

 hinge-teeth of the right valve speaks, there being in it only two diverging and 

 distinctly striated cardinal teeth present under the beak. 



Locality. — Near Arrialoor, in a soft whitish sandstone. 



Formation. — Arrialoor group. 



d. Group, — Quadrat(B. 



7. Trigonia crenipera, Stoliczka, PL XV, Eig. 13. 



T. testa sub-quadrangulari, paulo inflata, incequilaterali, antice hreviter rotun- 

 data, postice producta et ad terminationem late ac subrotunde truncata, siiperficie 

 costulis tenuibus paulo flexuosis omnino confertim crenulatis ornata, iis in area 

 perlata cum adjacentibus in regione ab apice ad marginem infero-posteriorem ex- 

 tensa positis angulos fere rectos formantibus. 



A very marked species, easily recognised by the numerous finely crenulated 

 ribs being present on the entire shell. The form is a little longer than most other 

 species of the '' Quadratce'' group, but the ornamentation is typical. 



Locality. — Olapaudy, in a brownish somewhat oolitic rock ; apparently very 

 rare. 



Formation. — Arrialoor group. 



XXXIV. Family —NVCJJLANILJF. 

 CLjedidjE, auctorum). 



The animals have the mantle margins almost entirely open, except posteriorly 

 for a very short distance, a narrow commissure separating a posterior siphonal 

 opening, through which partially, or almost wholly, united, retractile, siphons 

 can be protruded ; the exhalent siphon is occasionally represented by a simple 

 mantle fold; sometimes, as in Nuculana and Neilo, special appendages of the 

 mantle occur below the siphons ; these apparently assist in hatching the young, and 

 I doubt whether they are constant in the different species. There is one pair 

 of palpi on either side, they being elongated and pointed ; one pair of unequal 



