318 CPtETACEOUS PELECYPODA 



12-lG, lamelliformibus, acutis, distantibus, in decUvitate postica continuis, inter- 

 spatiis latis, haud profmidis, minutissmie striatis, notata. 



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

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

 minent, and wdth 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 TrUjoniu, only the " Glabrce" 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 Tngonia ; 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 teetli present under the beak. 



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



Formation. — Arrialoor group. 



d. Group, — Quadratce. 



7. Tkigonia crenifera, StoUczka, PL XV, Fig. 13. 



T. testa sub-quadrangidari, pa^Uo inflata, incequilaterali, antice breviter rotun- 

 data, jJOntice 2^roducta et ad termhiationem late ac subrotunde truncata, siq^erficie 

 costulis tenuibus paulo flexnosis omnino confertbn crenulatis ornata, iis in area 

 perlata cum adjaeentihus in regione ah apice ad marginem infero-posteriorem ex- 

 tensa posit is angidos fere rectos formantlbus. 



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— NUCULANID^. 



CLedidje, 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 cither side, they being elongated and pointed; one pair of unequal 



