nuculim:. 163 



elsewhere, smooth ou the umboes, but elsewhere with puckered 

 wrinkles of increase, which are very conspicuous below. Front 

 dorsal edge horizontal or rising, at first almost straight. Posterior 

 side almost excised, the hinder edge being almost perpendicular, 

 and the beaks, which, when not eroded, are acute and prominent, 

 being almost terminal. Ventral margin entire, subarcuated in 

 the middle, rising convexly at both ends. Lunular region much 

 and closely puckered, not strictly defined, yet concavely impressed 

 at its circumference, and often marked with a few irregular radi- 

 ating incised lines. Front dorsal region expanded, disposed to 

 be indented. — The hinge appears to resemble that of tenuis, but 

 I have not examined any example which was uninjured in that 

 respect. 



36. N. delphinodonta,* Mighels, f. 138, 139.— T. minima, 

 subobliqua, late ovato-trigona, ventricosa, cute nitidissima olivaceo- 

 virente vel olivaceo-lutea induta, inferne plicis planulatis subincli- 

 natis, sulcisque latis (aliquaudo etiam superne) concentrice sculpta. 

 Extremitas antica inferne rotundato-subangulata : latus posticum 

 fere nullum, inferne oblique retundato-excisum. Margo ventralis 

 integer, modice arcuatus. Nates valde promiuentes, ssepius erosae. 

 Lunula vix definita, rude et concentrice corrugata, valde prominens. 

 Area inconspicua. — Minute, of a rather oblique abbreviated ovate- 

 triangular shape, ventricose, especially behind, clothed with a po- 

 lished olivaceous-green or olivaceous-yellow epidermis, concentri- 

 cally divided near the lower margin by broad shallow sulci into 

 flattened and somewhat shelving folds : the sulci here and there 

 perceptible (but not regular) on the umbonal region likewise. 

 Anterior extremity subangulately rounded below : posterior edge 

 almost perpendicular. Ventral margin entire, moderately arcuated, 

 rising behind so as to obliquely round off the posterior corner. 

 Beaks much elevated, usually eroded. Lunular region very pro- 

 minent, undefined (at most a little impressed at its margin), 

 coarsely wrinkled concentrically. Front dorsal area undefined. 

 Hinge-margin broad : cartilage not at all horizontal : teeth three 

 or four, and seven to ten. 



* N. nana, Hinds, Proc. Zool. Soc, 1843, p. 98. — ■" T. minima, trigono-elliptica, 

 laevigata, nitida ; marginibus ventralibus minutissime crenulatis ; cardine antice den - 

 tibus 5, postice 11 ; umbouibus t'uscis. Long. 1 lin." This minute shell, said to 

 come from the Philippines, and described from Mr. Cuming's collection, must, I 

 suspect, have been lost ; for the three specimens named in that cabinet (f. 156) belong 

 to this species, and do not agree with their description. As Mr. Hinds omitted to 

 figure it, and the definition is wholly inadequate, the species may be regarded as too 

 uncertain to be retained. 



