39 



TAB. CCCCXXXI. 



Trigonia elongata. ('i/ar. T.coslata?) 



Spec. Char. Elongated gibbose subtriangular; 

 anterior side obtuse, transversely costated ; 

 posterior side separated from the anterior 

 by a crennulated carina, bicarinated, lon- 

 gitudinally striated, striae granulated. 



Syn. Trigonia costata (b.) Lam. Hist. Nat. 

 VI.pt. \.p.64. 



JVlucH doubt is experienced upon examining a number 

 of specimens of this Trigonia, they vary so considerably 

 in length, or rather in tlie inclination the iiinge line and 

 costae bear upon the large carina, and also in the form of 

 this carina ; and we are strongly inclined to believe with 

 Lamarck that it is only a variety of Trigonia costata 

 (Min. Conch, t. 35.) The costae are rounded and pro- 

 minent, they are rarely connected with the carina, 

 but they are more often separated from it by a furrow. 

 The carina is sometimes broad and low, sometimes it is 

 elevated moderately, and at others it is very prominent 

 and thin ; it is always more or less crenated. The an- 

 terior side has two lesser carinae, of which that nearest 

 to the hinge is the most elevated ; between them are 

 many strongly crenulated ridges. The beaks are 

 elegantly incurved. 



Two of the figures (1 and 2) upon this Plate are from 

 specimens found at Iladipole, near Weymouth and se- 

 lected from among several in the possession of our very 

 kind Friend Miss Benett ; at first sight they seem 

 very distinct from the T. costata of the IronsUot or in- 



