Report on the zoological collections made in the Indo-Pacific Ocean ...

98 COLLECTIONS PKOM MELANDSLA..22. Petricola lapicida.Venus lapicida, Chemnitz, Con.-Cab. x. p. 356, figs. 1664-5 ; Soiverhy,Conch. Icon. (I'etricola) figs. 22, 24 ; Martens in Von der Deckeri'sHeisen in Ost-Afrika, vol. iii. p. 66, pi. 3, figs. 3 a, b.Hah. West Indies {Chemnitz, cVOrhigny, Sfc); North Australia(/. B. Elsey in Brit. Mus.) ; West Island, Prince of Wales Channel,Torres Straits {Coppingcr) ; Zanzibar {Peters, teste Martens).This and the Venus divaricata of Chemnitz I regard as one species,and from his description of the former it seems probable that he hadbefore him specimens which to a great extent had lost the fine zigzagsculpture mentioned in his description of the latter. The raisedoblique ridges from the umbones down the posterior slope havevarious degrees of development in different specimens, in some existingonty near the posterior margin of the valves, whilst in others theyextend the whole distance from the beaks downwards, and, again, inyoung shells they may be altogether wanting. These ridges areeasily removed, and seem to be superimposed upon the zigzag sculpturebeneath. After a careful examination of Austrahau specimensand others from the West Indies, I cannot detect any materialspecific difi"erences.The example figured by Dr. E. von Martens as P. divaricata isunsually peaked at the umbones.23. Psammobia modesta.Deshayes, Proc. Zool. Soc. 1854, p. 319 ; Peeve, Conch. Icon. tig. 3.Hah. Port Jackson {Coppinger) ; Moreton Bay {DesJiayes).The single specimen before me is rather narrower than thatfigured in the Conchologia 'Iconica.' is purplish lilac within for themost part, yellowish near the muscular scars, and exibits the j^inkishrays on the ventral margin. The epidermis is brightish yellow.Oblique striae are sometimes present at the central portion of thevalves, but are not conspicuous.24. Psammobia gracilenta. (Plate VII. figs. B-B 2.)Shell concentrically striated, transversely elongate, very inequilateral,almost twice as long as high, not very compressed, dirtywhitish with a few diaphanous zones and several light reddishnarrow rays beneath a thin pale yellowish-olive epidermis, verynarrowly gaping at both ends. Anterior dorsal margin of the valvesabout twice as long as the posterior, subrectilinear, and nearlyparallel with the ventral. Hinder dorsal edge oblique, a littlearcuate. Lower margin straightish, obliquely curving upward infront and more sharply turning at the opposite extremity. Interiorbluish white, iridescent, exhibiting the reddish rays. Beaks small,adjacent, posteriorly inclined. Ligament short, but prominent, placedon a conspicuous ligamental plate in each valve behind the umbones.A second minute ligament exists immediately in front of them and