OF SOUTIIERX IXDIA. 89 



PANOP.EA, Memtrd, 1807 (see p. 85). 

 1. Panop.^a okientalis, Forbes, PL II, Fio-s. 1-i. 



1846. Panopaa orientalis, Forbes, Trans., Geol. Soc, Lond., vii, p. 139, &c.-ulem auctorum ; (nomen 

 P. orientalis, Con., (Off. Rep. iii Lynch 's Exped., Falsest., dubiosum). 



P. testa ovato-elongata, valde incequilaterali, parte aiitlca mnlto breviori, sulcu 

 lato sed hand profundo ah aplcibus ad marginem inferiorem suhrecte decurrente 

 separata, lateribus anteriorihus rapide declims, infra hiantibus ; parte jwstica 

 gradafim ^;Z?fs miuiisve atteniiata. ad termhiationem rotundata ac late hiante ■ 

 sttperjicie striis minutissimis ac sulcis costullsque angustis, wiprlmis prope apices- 

 distiuctis notata. 



Greatest height of shell : its length ... ... .,_ 0'64 



Thickness „ : „ ... ... ... 48 



. The form of the shell of this species is very characteristic, but as rei-ards 

 the posterior attenuation somewhat variable; the anterior part of the shell is 

 truncated in front and separated from the posterior by a broad, thouo'h shallow 

 furrow^ extending from the beaks to the antero-inferior margin. The middle portion 

 of the lower edge is convex ; the concentric sulcations are as usually most distinct 

 near the beaks ; the fulcra are long, thickened, but not very prominent. The rio-ht 

 valve has an erect tooth in front of a pit to which the tooth of the left valve 

 corresponds. 



Localities. — Anapaudy, Koloture, Serdamungalum, North of Alundanapooram, 

 &c., and south of Arrialoor ; mostly in Ijluish, brownish, and whitish sandstones. 



Formations. — Trichiuopoly and Arrialoor groups ; very common in the former, 

 rare in the latter. 



YII. Fumihj~GLA UCONOHIYID^F. 

 The animals of the species belonging to this family are, in external appearance, 

 very ^similar to those of the MYiy^ on the one side and the asatinin^ on the 

 other ; they have the mantle margins united, open anteriorly for the protrusion of 

 only a small, more or less elongated foot ; the gills are double, rounded, about 

 half the length of the body, and one-third longer than the palpi, which are broadly 

 falciform. The gills are not prolonged into the siphons* which are united up to 

 the end, with the orifice free and fringed ; they are enveloped in an extension of a 

 more or less thickened or coriaceous epidermis which covers the shell, similarly as 

 in 3Iya or Anatina. At the base of the siphons there is a very small openino- in 

 the mantle thi-ough which a portion of the water which enters the body is at 

 intervals ejected with force, while the current in the in-and ex-haling siphons is a 

 more regular and continuous one. A similar opening below the siphons is also 

 found in NovacuUna (and several other Solesjd^), serving the same purpose. 



er 



* In Glanconomya cerea, which is found along our sea coast, Mr. W. T. Blanford tells me the siphons are rath, 

 thin and of nearly double the length of the body. This coincides with an observation I lately made on a species 

 occurring on the sandy beach at Arracan. 



