EEPORT ON THE LAMELLIBRANCHIATA. 827 



in being concentrically sculptured and lacking the radiating ridges, usually spine-bearing, 

 which, so far as I am aware, are present ui)on the upper or free valve of every known 

 species. This absence of radiating sculpture, and the lamellated character of the 

 concentric lines of growth, gives this species very much the appearance of a small 

 oyster, which suggested the name Spondylus ostreoides. The inner margin of the valves 

 of most species of this genus are fluted, a style of sculpture occasioned by 

 the external ribbing. In the present form this generic character is main- 

 tained in a modified form, the upper valve having nearly all round, 

 somewhat remote elongate tubercles which fit into minute pits or 

 punctures in the other valve. 



Length 11 mm., height 14, diameter 6. 



Habitat— Station 170, July 14, 1874 ; lat. 29° 55' S.,long. 178° 14' E.; 

 depth, 520 fathoms; bottom, volcanic mud (north of the Kennedec '^ 



Spondylus ostreoides. 

 Islands). l, exterior; 2, inter- 



Most of the known species of Spondylus (with the exception of a few 

 brought up on telegraph cables) have hitherto been obtained in comparatively shallow 

 water. The absence of colour in the present form, and its depauperated condition, is 

 probably the result of existing in deeper and colder water than usual, and fine handsome 

 species are not to be expected from such localities. A fact worth mentioning in this 

 place is the presence, upon the upper valve, of a species of Polyzoa, which my colleague 

 ]\Ir. Quelch pronounces without doubt to be Crihrilina radiata (Moll.), a form found in 

 shallow water on the British coast. 



