REPORT ON THE LAMELLIBRANCHIATA. 81 



moderately convex, and sculptured with fine concentric lirse, which become more slender 

 at the sides, and are crossed chiefly on the hinder part by fine radiating striae. The 

 dorsal mai-gin is angled at the beaks, and descends about equally on both sides, the 

 posterior portion, however, being rather longer than the anterior. The ventral outline is 

 broadly arcuate, about equally ascendant on each side, and forms, together with the dorsal 

 slope, acutely rounded extremities at both ends. The beaks are not much elevated, small, 

 moderately acute, and curved over at the tip towards the hinder end. The hinge consists 

 of a central large triangular cartilage-pit in both valves, which in the right is bordered 

 in front with an erect oblique prominent tooth fitting into a corresponding deep groove 

 in front of the cartilage-pit in the left valve. The anterior of the valves has a short 

 ridge or thickening, which, arising beneath the umbones, descends to the inner side of the 

 anterior muscular impression. 



Length 5 mm., height 3|, diameter 2. 



Habitat. — Station 33, off Bermuda, in 435 fathoms; coral mud. Station 113a, 

 off Fernando Noronha, in 25 fathoms ; and Station 120, ofl" Pernambuco, in G75 fathoms. 



This species is very like Ervilia nitens, but apparently does not attain such large 

 dimensions. It is more finely concentrically striated and prettily cancellated down the 

 posterior side. In some instances, however, the radiating striaB extend more or less over 

 the entire surface. There are specimens in the British Museum from St. Thomas and 

 St. Vincent in the West Indies. 



Ervilia sandwichensis, n. sp. (PL XXV. figs. 5-56). 



Testa infe(]^uilateralis, compressiuscula, ovata, all^a, liris concentricis tenuibus aliisque 

 radiantibus concinne granoso-cancellata. Margo dorsi posticus leviter declivis, 

 rectiusculus vel levissime arcuatus, anticus longior, prope umbones j)eculiares tubercu- 

 liformes et rufescentes paulo concavus. Latera sequaliter subacute rotundata ; margo 

 ventris late arcuatus. 



This species is pure white, with the exception of the minute tuberculiform embryonic 

 tips of the umbones, which are of a reddish tint. It is transversely ovate, equally and 

 rather sharply rounded at the sides, and broadly curved beneath. It is somewhat 

 compressed and inequilateral, and sculptured with numerous slender concentric lirae, and 

 others which radiate from the beaks, forming a very pretty cancellated surface, as the 

 points of intersection are more or less nodulose. 



The structure of .the hinge is normal as in Ervilia castanea. The interior is very 

 glossy, and, owing to the transparency of the shell's texture, the external ornamentation 

 is visible. 



Length 3 mm., hieght 2, diameter \\. 



Habitat — Off the Reefs at Honolulu, Sandwich Islands, in 40 fathoms. 



(ZOOL. CHALL. EXP. — PART XXXV. 1885.) Mill 11 



