114 THE VOYAGE OF H.M.S. CHALLENGER. 



There appears to me little doiibt that the above so-called species are ])ut variations of 

 one and the same form. I do not find any distinguishing characters in the outline or the 

 sculpture, all are finely concentrically sulcate-striate towards the umbones, the grooving 

 becoming gradually stronger and further apart as the shell enlarges, especially towards 

 the hinder end of the valves. The posterior dorsal margin is well arched, curving into 

 the lateral outline without any perceptible angle. In addition to the concentric sculpture, 

 there are generally (not always) traces of faint radiating substrise, more or less visible 

 when the shell is viewed in certain positions. The colour-ornamentation may vary in 

 intensity and definition, but in general arrangement and character it is the same. 

 AU the varieties exhibit four more or less well-pronounced and interrupted rays, besides 

 a somewhat zig-zag reticulation of dark lines very indistinct in the type {Tapes ohscurata), 

 more apparent in the variety Tapes grata, and most conspicuous in the form named Tapes 

 quadriradiata. 



The ornamentation of the lunule is fairly constant in all. It consists of short violet- 

 brown lines crossing transversely to the length. They do not extend beyond the 

 impressed circumscribing line, and consequently the lunule has a very clear definition. 



The posterior dorsal area is also somewhat similarly marked, but not so distinctly, 

 the colour of the lineation being rather paler. The dark blotch or stain near the centre 

 of this portion of the surface, mentioned by Deshayes and Romer in their descriptions 

 of Tap)es quadriradiata, is also traceable in Tapes ohscurata and Tapes grata, although 

 unnoticed by the latter author, and indeed in all specimens there is a second smaller 

 blotch nearer the umbones. Tapes similis of Deshayes ( = Tapes grata of Eeeve and 

 Romer) I regard merely as a small, finely sculptured form of the West African Tapes 

 dura of Gmelin. The Tapes ohscurata of Romer does not apparently belong to the 

 present species, nor do I consider his Tapes similis the same as Tapes grata, Deshayes. 



Reeve in his monograph of this genus reversed the names of these two last species, 

 his Tapes similis being in fact the type of Tapes grata, and his fig. 9 representing the 

 true Tapjes similis. This confusion has no doubt misled Romer in his identifications. 



Tapes [Paratapes) textrix (Chemnitz). 



Venus textrix, Chemnitz, Conch.-Cab., vol. vii. p. 48, pi. slii. fig. 442. 



Tapes textile, (Gmelin) Sowerby, Thesaurus, vol. ii. p. C81, pi. cxlvi. figs. 26-28. 



Tapes textrix, Eeeve, Conch. Icon., vol. xiv. fig. 3. 



Tapes textrix, Eomer, IMonogr., p. 19, pi. v. fig. 1. 



Habitat. — Port Jackson, New South Wales, in 4 to 18 fathoms. 



Specimens from this part of the coast of Australia differ slightly from Indian Ocean 

 examples in the style and tone of the painting, agreeing better with Tapes undulata 

 than with Tapes textrix. The upper part of the valves is of a pale yellowish-brown tint 



