56 Proceedings of the Royal Physical Society. 



morpha, by Dr Stoliczka, * and with another genus of 

 M'Coy, Scclgwickia, by the late Dr S. P. Woodward.f The 

 second group, typified by L. costellatus, Dr Stoliczka thinks 

 may be identical with Plectomya of Loriol. j Whatever may 

 be the eventual designation of the last species, the name 

 Leptodomus must, if retained, be applied as originally defined 

 by M'Coy. If distinct from Sedgioickia, it must be used in 

 this sense ; if identical, the name may then justifiably be 

 transferred to the L. costellatus section, provided further 

 researches show this shell to be distinct from any other 

 previously described genus. 



In the limitation of the three next genera great confusion 

 exists. This is owing to the misapprehension of structure 

 on the part of one or other of their authors, aided by an 

 almost identical date of publication, by which they were not 

 acquainted with the works of one another. Edmondia 

 (De Koninck) is the best defined and most reliable. It is a 

 transversely-oval, equivalve, edentulous shell, with an inter- 

 nal lamellar cartilage support. The dorsal margins are erect 

 and simple, and the pallial line entire. As typified by 

 E. unioniformis (Phill.) it forms a fitting receptacle for many 

 Carboniferous Bivalves. Professor W. King has instituted 

 a separate family for this genus, the EdmondiidcTS. 



The most perplexing of these genera is Sanguinolites 

 (M'Coy), which, if sufficiently restricted, will be found to 

 embrace many well-marked shells. At present it is a 

 Heterogenous assemblage of such species, others referable 

 to Edmondia, and some appertaining to the next to be 

 noticed, Allorisma.^ Sanguinolites was described in 1844,11 

 on the type of Phillips' Sanguinolaria angnstata, but the 

 original example of this, in the Gilbertson Collection, is in 

 so bad a state of preservation, that it will be next to impos- 

 sible to say what is, or is not Sangninolites, as typified by it. 

 The shells to which the name will probably have to be re- 

 stricted, are traversely oblong and equivalve, but very inequi- 

 lateral, possessing an external ligament, and a strong external 

 oblique posterior ridge. The pallial impression is entire. 



* Tal. Indica, p. 270. t Man. Mollusca, p. 322. t Loc. ciL, p. QQ. 

 § King, Mon. Term. Foss., p. 161. |1 M'Coy, Synopsis, p. 47. 



