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



tluiii the rest. The posterior auricle of the right valve is large, and has about ten fine 

 riblets, that of the left valve is deeply sinuated below, truncated at the end, and sculp- 

 tured with fine ridges (the marginal one being the largest) covered with closely packed 

 transverse squamulse. The portion of the sinus filled u]) during the growth of the shell 

 is white, somewhat concave, and crossed by coarse elevated lines of growth. The inner 

 surface of the valves is glossy, tinted like the exterior, and finely grooved and ridged ; 

 or, in other words, exhibits a reversal of the external ornamentation, the grooves 

 corresponding to the ridges of the exterior and the ridges to the intervening sulci. 



Length 22i mm., height 24|, diameter 63. 



Habitat. — Station 141, ofi'the Cape of Good Hope, in 98 fathoms; also Station 135, 

 ofi" Nightingale Island, Tristan da Cunha group, in 100 to 150 fathoms. 



In the earliest stage this shell is smooth or only microscopically striated by lines of 

 growth. It then assumes a second style of ornamentation, consisting of fine wavy 

 radiating wrinkles which run in among the incipient cost8e. To this wrinkling succeeds 

 the fine concentric striae, which subsequently become more remote and less pronounced. 



The Challenger shells above described do not correspond precisely with the single 

 type specimen of this species in the British Museum. This formed part of the Cumingian 

 collection, and, like the majority of Mr. Cuming's specimens, has been spoilt through over- 

 cleaning, nearly aU the microscopic sculpture being destroyed. It diflers from the shells 

 under examination in having the posterior ear of the left valve slightly larger, and the 

 scales upon the riblets rather fewer. Both valves, but especially the right, have a number 

 of dark and pale brown spots, due probably to living in shallower water than the 

 Challenger specimens. 



(?) Pecten lenmiscatus, Keeve. 



Pecten lentiginosus, Reeve, Conch. Icon., vol. viii. pi. xxxv. fig. 170 {non species 76). 

 Pecten lemniscatus, Reeve, op cit., Errata at end of Index. 



Habitat. — Samboangan, Philippine Islands, on Reefs, in 10 fathoms. 



The single Challenger shell is considerably like the t3rpe in the British Museum, but 

 exhibits in the grooves between the ribs a fine shagreen-like sculpture which I do not 

 find in the specimen referred to, the only one I have been able to examine, and which, 

 having been rather over-cleaned, may have lost its more delicate ornamentation. 

 Reeve's description of the right valve is not altogether clear. He says it is " ecostata, 

 undique lirata, squamis brevibus abrupte nodulosis." The ridges are in fact more equal 

 in thickness than in the other valve, of which in size they about equal the smaller ones. 

 They are closely squamate, and the scales being worn off' to a great extent have to the 

 naked eye a finely nodulous appearance. 



