54 



IRIDINA. 



GENUS PLATIEIS. 1 



I. SUBGENUS IRIDINA.* 



OBOVATE. 



ovata. Swain. 

 Irid. exotica. Children. 

 Pleiodon Macmurtriei. Con. 



*Leaii. 3 Sow. 



ARCUATE. 



exotica. Lam. DesJi." Pot. 



M 



' 



55 









P 









« 













w -1 





Ph 













w 





m 





fe 





O 





fc 





ARCUATE. 



Jri'd. striata. Swain. 

 Irid. elongata. Sow. 

 An. exotica. Plain. 



Species Unknown. 

 Iridina valeus. Parr, from Africa, in 

 Jag's Cat. 



1 Genus Platiris (nobis), n^arus, latus; 1515, iris. Testa sequivalvis, late transversa; impressiones musculares 

 grandes; cardo longus, linearis; ligamentum externum. 



a When Lamarck established his genus Iridina, he had seen but a single species, and of that only one indi- 

 vidual, which is figured in the Encyclop. Methodique, PL 204. Other species have been since referred to his genus, 

 which do not seem to me to fulfil the conditions of his generic diagnosis. The phrase " cardo per longitudinem 

 tuberculosus, subcrenatus," is by no means descriptive of the hinge belonging to the species just alluded to, which 

 have their hinge smooth, or very slightly tuberculated. The figure in the Encyclopaedia, and that of Blainville 

 (PL 66, Fig. 3), represent the same individual, and exhibit a character of hinge resembling in some measure that 

 of an Area. A second species, apparently agreeing with Lamarck's generic description, has been observed and 

 described by Swainson, under the name of Iridina ovata {Phil. Mag., vol. lxi.) ; and it has also been described by 

 Mr. Children under the name of I. exotica {Branch's Journ., vol. xv.). The specimen described in Brand's 

 Journal is now in the British Museum, and that accurate naturalist, Mr. John Edward Gray, who is one of the 

 officers of that noble institution, informs me that he thinks it is identical with the shell upon which Mr. Conrad 

 has lately proposed to form a new genus, Pleiodon. Under these circumstances, it seems to me necessary to separate 

 those shells having a crenulated hinge (which are true Iridinee), from those having the hinge smooth, or very slightly 

 tuberculated. I therefore arrange the Iridina rulens, Nilotica, &c., in a new subgenus, for which I propose the 

 name of Spatha. 



Ferussac says that Humphrey, in his Catalogue (MSS. ?), made a genus {Scapha) for an Iridina, and that the 

 "mutel, D'Adanson," is certainly the same {Mem. de V Hist. Nat. cle Paris, v. i. p. 362). 



3 Mr. Sowerby very kindly presented me with a specimen under this name. It looks to me like a young 

 I. ovata, but may be different. 



4 M. Deshayes gives the Nilotica as a synonym to this species^ but I think it is distinct. 



