228 Mr. E. A. Smith on the Genus Pytliina. 



centre. Nothing is known of tlie animal of this interesting 

 shell. 



As many as nineteen so-called species have been described 

 as belonging to this genus, or have been subsequently placed 

 in it. Some of these do not possess the remarkable sculpture 

 which characterizes the type, and differ also as regards the 

 construction of the hinge. Others agree in having divaricate 

 plications, but exhibit a widely different dentition. 



I will now proceed to discuss each of these species, and will 

 indicate the genus to which I think they should be referred. 



1. Pytliina Deshayefiiana^ Hinds. 



1844, Pythina Deshayesiana, Hinds, Zool. Voy. ' Siilpliui'/ vol. ii. p. 70, 



pi. xix. figs. 8, 9. 

 1858. Ptjthina Deshayesiana, H. & A. Adams, Gen. Rec. Moll. pi. cxiv. 



figs. 9, 9 a. 

 1862. Pythina Deshayesiana, Chenu, Man. Concli. vol. ii. p. 126, fig. 603. 

 1878. Pythina Deshayesiana, Kobelt, Illust. ConchyKenbuch, p. 352, 



pi. ciii. fig. 3. 



Eah. New Ireland {Hinds); also Philippine Islands 

 [Cuming, fide Hinds). 



In my report upon the Lamellibranchiata of the ' Chal- 

 lenger' Expedition, p. 204, I have stated that the dentition 

 of this species " is exactly that of KelUa " *, and that " the 

 fact of the shell being divaricately plicate does not in ray 

 opinion entitle it to generic rank, but may be regarded of 

 subgeneric importance." I have again critically examined 

 this species, with the result that I am able to confirm the 

 above observations, perha])S modifying the last statement 

 respecting the relative value of sculpture in separating genera 

 or subgenera. I am now inclined, in this instance, not to admit 

 that it is even of subgeneric importance. 



The dentition of this species is accurately defined by Hinds, 

 H. & A. Adams, and Kobelt ; but Chenu, in his ' Manual,' 

 has described the hinge of Mi/Jitfa, being under the im])ression 

 that it was synonymous with Pythina. Hinds states that the 

 pallial line is without any sinus ; and on examining three 

 specimens in the British ]\Iuseum I find this to be correct, 

 for the regular uninterrupted impression is clearly traceable 

 from scar to scar. On the contrary, the existence of " a slight 

 triangular sinus " is mentioned by H. & A. Adams and 

 Kobelt. This error may have arisen through those authors 

 obtaining tiicir information from the descrijition of Mylitta 

 (regarded by tliem as synonymous with Pythina) given by 



* Stoliczka has rotstriclcd Lamarck'.-* otunprolioiisivo genus Erycina and 

 made it equivalent to Kellia (I'aljedut. Indica, vol. iii. p. 2()3). 



