NUCUWDiE. 147 



the swollen and projecting umboes. Ventral margin arcuated, 

 convexly rising, without letusion, at both ends. Inside almost 

 pearly : cartilage-pit almost perpendicular, on either side of it 

 about ten teeth. 



73. L. sulcifera, Reeve, f. 165, 1G6. — T. subtequilateralis, sub- 

 anguste ovata, nisi ad umbones gibbosos compressa, ant ice rotun- 

 data, postice obtuse rostrata et paululum flexuoso-concava ; cute 

 corneo-virente induta, sulcis remotis longitudinalibus vix insculpta. 

 — Somewliat narrowly ovate, compressed, yet rather gibbous at the 

 umboes, subequilateral, rounded in front, slightly flexuous-con- 

 cave and bluntly beaked behind. Surface with distant superficial 

 longitudinal grooves. Epidermis greenish horn-colour. — Never 

 having seen this shell, the description is not original. 



NUCULA, Lamarck (restricted) . 



Gen. Char. More or less subtriangular, very inequilateral, closed 

 at one and usually at both ends, clothed with an epidermis : um- 

 boes turned to the shorter side.* Inside pearly ; margin some- 

 times crenulated : hinge-margin with a row of produced and 

 pointed interlocking teeth on either side of the projecting support 

 for the narrow triangular cartilage-pit, which slants to the longer 

 side. No pallia! sinus. 



Sect. A. Ventral margin crenulated. 



1. N. decdssata, Sowerby, f. 109, 110, 111. — T. valida, vix 

 obliqua, longitudine latitudinem multo superante, ad umbones 

 prominentes subrectangularis, subventricosa, cute luteo-vireute 

 induta, rugis lamellaribus coucentricis lineisque elevatis deusis 

 radiantibus arete et undique decussata. Margo ventralis crasse 

 crenatus. Lunula satis magna, protrusa, exteriie subgrauoso- 

 corrugata, superne laevigata. Area subplanulata, saepius trans- 

 versim plicato-corrugata (rugis eetate obsoletis). — Very variable in 

 shape and degree of lateral inequality, nearly rectangular at the 

 beaks, not particularly oblique, much longer than broad, subven- 

 tricose, nearly evenly diminishing in convexity on either side, 



* When there is neither a pallial sinus, nor an external ligament, it is usual to 

 consider that side the posterior which contains the larger portion of the cartilage, and 

 that the anterior towards which the beaks incline. The position of the animal in 

 Nucuta, however, compels me to term the shorter end the posterior. The words lunule 

 and escutcheon are here used with their ordinary signification, and not as equivalent 

 to front and hinder dorsal impression. 



