108 nucdlidjE. 



and are cross-hatched, as it were, by true concentric ones. Sides 

 equal, or very nearly so. The front extremity bluntly rounded ; 

 the beaked hinder side gradually attenuated to a very narrow, 

 rather oblique, truncated, recurved tip. Front dorsal edge straight- 

 ish, nearly horizontal; hinder dorsal slope slight, much incurved. 

 Ventral margin arched in front, much and convexly rising behind, 

 neither refuse in front nor centrally. Escutcheon excavated, 

 large, carinately defined by the projecting, nearly simple (i.e. not 

 distinctly crenulated) edge of the umbonal ridge, which latter is 

 planulate, and inconspicuous. Lunule narrow, not well defined. 

 Cartilage-pit broadly triangular. Teeth very numerous on both 

 sides. 



4. L. Tellinoides, Sowerhy, f. 36. — T. lanceolato-elliptica, 

 antice rotundato-acuminata, flexuosa, subaequilateralis, nivea, com- 

 pressa, nisi postice undique striata : striae anticse longitudinales ; 

 mediae oblique curvatae. Margo dorsalis uterque vix declivis, an- 

 ticus plano-convexus, posticus vix retusus. Area? dorsales incon- 

 spicuai. — Elongated, lanceolated-elliptic, slightly fiexuous, bend- 

 ing down a little in front, and inclining upwards a little behind ; 

 thin, glossy, snow-white, compressed ; smooth behind, elsewhere 

 striated : striae curved and slanting in the middle, almost concen- 

 tric in front. Sides very nearly equal, gradually and nearly equally 

 tapering to either extremity ; anterior end rotundately peaked ; 

 posterior end angular above, rounded below. Dorsal slopes very 

 slight ; the front oue plano-convex, the hinder one barely subre- 

 tuse. Ventral margin subarcuated throughout, with an extremely 

 slight anterior, and no posterior, retusion. Dorsal areas incon- 

 spicuous ; the hinder one impressed, its edges minutely crenulated. 

 Teeth very numerous on both sides. — Besides the longitudinal 

 striae, a few symmetrical lines of growth may be discerned beneath 

 the front dorsal edge, and a few still more indistinct ones (but no 

 striae) on the opposite side. In mature examples similar lines are 

 likewise manifest in the middle, near the lower margin. 



5. L. gloriosa, A. Adams, f. 42, 43. — T. anguste lanceolata, 

 nivea, in medio tantum inferne compressa, ante radium iinpressum 

 anticum plicis planulatis latis, et pone eum striis inclinatis arctio- 

 ribus, concentrice sculpta; postice multum longior, obtuse acu- 

 minata, incurvatione utriusque marginis coarctata. Margo dorsalis 

 anticus plano-convexus vix declivis ; ventralis antice arcuatus. — ■ 

 Elongated lanceolate, snow-white, shining, gaping at both ends 

 (especially below anteriorly), convex or subventricose, rctusely 

 compressed below in (he middle, with an indented ray in front; 



