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



and fits, as it were, within the other valve, its very thin margin being npcurved and 

 api^ressed to the outer edge of the other valve. It is sculptured with a few lines of 

 gro\\i:h, and has under the microscope a minutely shagreened appearance. The left valve 

 is much deeper, and ornamented with coarse concentric lamellae, which, crossing about 

 seven or eight strongish radiating \ivsd, produce a coarsely cancellated surface. The 

 ears in this valve have only the concentric lamellse and are al)0ut equal in size, the 

 posterior being sinuated at the side. The anterior auricle in the right valve is orna- 

 mented with concentric lamellae of growth which cross a few radiating ridges, and it is 

 rather deeply cut in beneath. The hinge-line occupies the whole length of the shell, and 

 above the centre the umbo of the left valve is slightl)^ prominent. 



Length 2 mm., height 1|, diameter |-. 



Hahitat. — Prince Edward Island, in 100 to 150 fathoms. 



The shell here described is probably not adult ; but as the sculpture of the valves is 

 so markedly different and not like that of any other species with which I could compare 

 it, I do not think it hazardous to name it. 



Pecten culehrensis, n. sp. (PL XXII. figs. G-Go). 



Testa compressa, paulo insequivalvis, teuuissima, semipellucida, altior quam longa. 

 Valva dextra parum convexa, lamellis numerosis concentricis, plus minusve radiatim 

 squamulatis, ornata. Valva sinistra leviter convexior, liris tenuibus radiautibus et 

 concentricis confertim cancellata, et nodulosa. Auriculae inaequales ; antica valvas dextrae 

 superne cristata, ratliatim lirata, inferne mediocriter profunde sinuata. 



This is a very compressed species, very thin, semitransparent, slightly inequivalve, 

 and higher than long. The right valve is a little flatter than the left, and sculptured 

 with numerous fine concentric lamellae which are more or less ornamented with small 

 scale-like projections disposed in radiating series. When these are broken off the lamellae 

 have a frilled appearance. The left valve has a somewhat coarser sculpture, which 

 consists of slightly stronger concentric lira3 and numerous radiating ones, some of which, 

 at irregular intervals, are thicker than the rest, the points of intersection of all, but 

 especially the stronger ones, with the concentric lirse being jjrettilj^ nodulose. The ears 

 are rather unec^ual, the anterior as usual being the larger. That of the right valve is 

 rather strongly sculptured with lamellae of growth (produced above into a crest along the 

 hinge-line) and a few somewhat feeble radiating ridges. The umbones are rather acute, 

 having the sides, of which the anterior is rather straighter than the posterior, converging 

 to an apical angle of about 95 degrees. 



Length 8^ mm., height 9^, diameter 2|. 



Habitat. — Station 24, off Culebra Island, AVest Indies, in 390 fathoms ; Pteropod ooze. 



