OE SOUTHERN INDIA. 55 



nent ; these teeth are comparatively narrow in the young shells, but in adult 

 specimens attain an unusually large size ; pallial line unknown." Type Fs. Gahbii 

 Rem. sp., from tertiary deposits of California. There is a cretaceous species 

 described by Midler as Cardimn Nijggeratlm. Its hinge strongly reminds one of 

 Gabb's Fseudocard'mm, but I have as yet only seen the hinge of the l-io-ht valve, 

 and this is not sufiicient for a correct generic determination. 



23. Ifactrodesma, Conrad, 1868, (Amer. Journ. Conch., vol. IV, p. 247). Shell 

 sub-triangular, solid ; .cartilage-pit very large, projecting much beyond the lower 

 margin of the hinge ; anterior hinge-margin of right valve thick and continued 

 much beyond the beak ; hinge of left valve with a strong A -shaped cardinal tooth; 

 lateral teeth short, thick, sub-equal ; pallial sinus narrow and deeper than in Iluctra, 

 but extending as far as the cartilage-pit ; muscular scars very large. Type Mactra 

 ponderosa, Conrad, (Fossils tert. format., 1838, p. 25, pi. 14, fig. 1), from the 

 miocene beds of Maryland. 



24. Bcingia, Desmoul., 1832. Shell sub-triangular, thick, covered with a 

 brown epidermis ; hinge with two teeth in each valve, the front one of left valve 

 larger and bifid ; lateral teeth elongated, transversally striated, ligament internal 

 situated at the upper edge of the cartilage-pit ; pallial sinus short. This is the 

 brackish representant of the mactrin^; the shell externally greatly resembles 

 some species of Unto. The oldest species of Mangia appears to be one noticed by 

 Dunker from the Wealden deposits, as GnatJiodon Valdensis, (Wealden-bildungen, 

 p. 57). 



24«.* Rangianella, Conrad, 1867 (Amer. Journ. Conch., vol. iii, App. p. 30,) 

 is characterized by "lateral teeth, straight, sub-equal, not elongated, entire;" the 

 only species is R. trigona. Petit. 



List of cretaceous species, 



LUTRARIINM. 



For the correction of those species which have been described from cretaceous rocks under 

 the generic name of Lidraria, see Pictet's Pal. Suisse, IV™^ Ser., S^^pt., p. 126. Not a single one of 

 those species has been shown to belong to this sub-ftimily. Gabb (Palajont. of Calif., 1864, vol. 1, 

 p. 154), describes and figures a Lutraria lrimcala,w\iK\i appears to me to be rather a Spisula than 

 a Lutraria. 



The four species, Lutraria speciosa, cuneata, naralis anilongiissima, (Schafhajutl's Bayeru's Leth. 

 geog., p. 173 et.) are not Lutraria, but either Iloi/iomyce or Panojieece. 



MACTRINJi:. 



Of most of the European species quoted by Pictet and Campiche (1. c, p. 128, &c.,) under the 

 genus Mactra, the determination has been made from external appearance only, and in many cases 

 it still requires confirmation. The species arc — 



1-7. — M. Matronetisis, Valangiensis, Carteroni, gaultina, sub-striata, angulata, porreda. 



* Meek (Smiths. Misc. Coll., No. 183, p. 11,) also quotes a sub-genus Perissodon. 



