98 COLLECTIONS FEOM MELANESIA. 



22. Petricola lapicida. 



Venus lapicida, Chemnitz, Con -Cab. x. p. 356, figs. 1664-5 ; Sowerby, 

 Conch. Icon. (Petricola) figs. 22, 24; Martens in Jw der Decken's 

 Eeisen in Ost-Afrika, vol. iii. p. 66, pi. '■'>. figs. 3 a, b. 



Hah. AVcst Indies (Chemnitz, d'Oirbigny, S[C.)', North Australia 

 (J". P. Elsey in Brit. Mus.) : ^'est Island, Prince of Wales Channel, 

 Torres Straits (Copjnnger) ; Zanzibar (Peters, teste Martens). 



This and the Vt nus divaricata of Chemnitz I regard as one species, 

 and from his description of the former it seems probable that he had 

 before him specimens which to a great extenl had lost the fine zigzag 

 sculpture mentioned in his description of the latter. The raised 

 oblique ridges from the umbones down the posterior slope have 

 various degrees of development in different specimens, in some existing 

 only near the posterior margin of the valves, whilst in others they 

 extend the whole distance from the beaks downwards, and, again, in 

 young shells they may be altogether wanting. These ridges are 

 easily removed, and seem to be superimposed upon the zigzag sculp- 

 ture beneath. After a careful examination of Australian specimens 

 and others from the West Indies, I cannot detect any material 

 specific differences. 



The example figured by Dr. E. von Martens as P. divaricata is 

 unsually peaked at the umbones. 



23. Psammohia rnodesta. 

 Deshaijes, Proc. Zool. Soe. 1854, p. 319 ; Peeve, Conch, Icon. fig. 3. 



Hah. Port Jackson (Coppinger) ; Moreton Bay (Deshayes). 



The single specimen before me is rather narrower than that 

 figured in the ' Conchologia Iconica.' is purplish lilac within for the 

 most part, yellowish near the muscular scars, and exibits the pinkish 

 rays on the ventral margin. The epidermis is brightish yellow. 

 Oblique strise are sometimes present at the central portion of the 

 valves, but are not conspicuous. 



24. Psammobia gracilenta. (Plate VII. figs. B-B 2.) 



Shell concentrically striated, transversely elongate, very inequi- 

 lateral, almost twice as long as high, not very compressed, dirty 

 whitish with a few diaphanous zones and several light reddish 

 narrow rays beneath a thin pale yellowish-olive epidermis, verj 

 narrowly gaping at both ends. Anterior dorsal margin of the valves 

 about twice as long as the posterior, subrectilinear, and nearly 

 parallel with the ventral. Hinder ' dorsal edge oblique, a little 

 arcuate. Lower margin straightish, obliquely curving upward in 

 front and more sharply tinning at the opposite extremity. Interior 

 bluish white, iridescent, exhibiting the reddish rays. Beaks small, 

 adjacent, posteriorly inclined. Ligament sin irt, but prominent, placed 

 on a conspicuous ligament al plate in each valve behind the umbones. 

 A second minute ligament exists immediately in front of them and 



