EEPORT ON THE LAMELLIBRANCHIATA. 181 



Habitat.— Station 188, south of New Guinea, in 28 fathoms (Challenger); Hong Eong 

 Harbour (Gould). 



There are two or three species which are so closely allied that if a large series of speci-^ 

 mens were got together, in all probability it would be difficult to draw any lines of separa- 

 tion. All are very similiar in form, agree in having a strong depression down the hinder 

 side of the valves and a feebler one in front, and differ chiefly in the coarseness of the 

 cancellation of the surface. Lucina pisum, Reeve, from Port Essington, is the most strongly 

 sculptured of all, the radiating costse being few in number, and as coarse or even coarser 

 than the concentric ridges. Lucina semperiana, Issel, has more numerous and more 

 slender radiating riblets than the preceding species, and its concentric ridging is of a 

 stronger character than the riblets ; and finally, Lticina seminula, Gould (judging from a 

 specimen in the British Museum which had been compared with Gould's type), is 

 ornamented with still finer concentric ridges and less conspicuous cross costellee. All 

 three forms have very deep lunules, especially Lucina pisum, and a peculiarly raised- 

 posterior dorsal area. 



Lucina ( Codahia) pisum, Reeve. 



Ludna pisvm, Eeeve, Conch. Icon., vol. vi. pi. xi. figs. 66, a, h. 

 Lucina pisum, H. and A. Adams, Genera Eec. Moll., vol. ii. p. 467. 



Habitat. — Station 188, south of New Guinea, in 28 fathoms (Challenger) ; Port 

 Essington (Jukes in Brit. Mus.); Singapore, in sandy mud, at a depth of 7 fathoms 

 (Cuming). 



The radiating costiB in this species are only about eleven in number, very strong, 

 and crossed by about sixteen stout concentric ridges, which are somewhat nodose upon the 

 costse, and gradually attenuated at both ends, which are devoid of longitudinal ribs. 

 The lunule is small but remarkably deep, and wider than long. The inner edge of the 

 valves is very strongly dentate along the lower margin, and very minutely crenulated at 

 the posterior truncated side. 



Lucina [Codahia) levukana, n. sp. (PL XIII. figs. 6-6a). 



Testa minuta, mediocriter crassa, oblique ovata, in?equilateralis, alba, convexiuscula, 

 lunula profunda instructa, liris tenuibus concentricis, aliisque radiantibus in interstitiis 

 multo tenuioribus ornata. Margo dorsi anticus oblique excavatus, posticus rectiusculus, 

 declivis. Latus anticum latum, rotundatum, posticum angustius. Umbones mediocriter 

 producti, ad apicem incurvati, antice versi. Lunula profunda, margine elevato indistincto 

 circumdata. Dentes cardinales valvse sinistrse duo crassi, divergentes, subfequales ; 

 laterales validi, remoti. Margo valvarum internus minute denticulatus. Ligamentura 

 internum, angustum, in sulco profundo positum. 



