REPORT ON THE LAMELLiBRANCHIATA. 265 



obliquely truncate. The dorsal liue is not quite so long as the entire shell, owing to 

 the obliquity of the hinder side. The valves exhibit a very faint de[)ression down the 

 middle, which causes the ventral margin to have a slightly incur^^ed appearance at that 

 point, and at the posterior end, behind a prominent crested ridge or angle radiating 

 from the umbones to the lower hindmost extremity, they are conspicuously concave. 

 The sculpture consists of strong imbricating lamellse and radiating ridges. TJic former 

 are most conspicuous, frilled on crossing the ribs, and produced into short, hollow spines 

 on the posterior angle. The radiating ridges are about twenty-five to thii'ty in number, 

 most crowded a little in front of the centre, coarsest and farthest apart just in advance 

 of and iipon the oblique keel, from which those on the hinder concave surface radiate, 

 and not from the umbones like the rest. The ligameutal area is narrow, broadest 

 towards the front, and gradually tapering backwards, but not extending to the end of 

 the dorsal line. The umbones are small, hardly half a millimetre apart, curved over at 

 the tips, and situated at a])out two-sevenths of the entii-e length of the shell, from the 

 anterior extremity. The inner surface of the valves is white, a little glossy, showing, 

 indications of grooving, corresponding to the external sculpture, and on each side under 

 the hinge-plate the muscular scars, of whirh the posterior is the larger, are conspicu- 

 ously white and thickened. The hinge-plate is not very In-oad, and bears about sixteen 

 teeth, which are placed obliquely towards both ends ; and, under the microscope, appear 

 roughly striated. 



Length 10 mm., height 5, diameter 5. 



Habitat. — Station 201, off the west coast of Mindanao, Philippine Islands, in 82 

 fathoms ; stones and gravel. 



This species is closely related to Area (loiningeusis, but may be at once distin- 

 guished by its.l)road truncate posterior end. 



A7va (Acar) domingensis, Lamarck. 



Area dominrjensis, Lamarck, Anim. sans vert., ed. 2, vol. vi. \k 467. 

 Area dominr/eims, Lischke, Jap. Mceres-ConcL, part ii. p. li'2. 



Habitat.— Station 36, off Bermuda and 8t. Vincent, Cape Verde Islands, in ;]0 



fathoms ; coral. 



For the remarkable distribution of this species, and some interesting observations on 

 the synonymy, consult the above work by Lischke. 



Area [Scapharca) angicostata, Reeve. 



Area angicostata, Reeve, Conch. Icon., vol. ii. pi. i.^. tig. 57. 

 Habitat. — Station 212, south of the Island of Mindanao, Philippines, in 10 fathoms ; 

 sand. 



(ZOOL. CHALL. ESP. — r.^KT .X.K.XV. — 18t>5.) ^Ini 3t 



