58 NUCUUD/E. 



olivaceous-yellow to ashy-olive, smooth, yet with strongly marked 

 wrinkles of increase. Ventral margin entire, arcuated (the arch 

 very prominent just before the middle), rising somewhat more 

 straightly behind, so as to form a rounded-ofl' obtuse angle with 

 the straightish or somewhat convex, rather abrupt posterior edge. 

 Front dorsal edge just at first straightish, and subhorizontal, then 

 much curved and descending. Posterior side very short, projec- 

 ting below. Dorsal areas wholly undefined ; lunular lips pouting. 

 Beaks very small, bent much forward, scarcely prominent, yet 

 conspicuous from their acuteness. Front hinge-margin sunken 

 internally. Teeth (in the adult) about fifteen and seven or sixteen 

 and eight ; the front ones scarcely vaulted, and near the extremity 

 compressed and seated on the inner edge. When not quite mature 

 a rounded off^ very obtuse, angle is exhibited at the front dorsal 

 corner. 



34. N. mYhkTh, Hancock, f. 115, 116. — T. sp. prfecedenti simil- 

 lima, sed magis trapezoeformis, (seepiusbrevior) ventricosa vel tumida, 

 umbonibus inflatis, prominentibus, cute sordide luteo-virente, vel 

 olivaceo-brunnea. Margo ventralis neque ante medium notabiliter 

 arcuatus, nee postice conspicue acclivis. Extremitas postica ab- 

 rupt e truncata, baud inferne eminens. Lunula inferne planulata. 

 — Closely resembling leiinis, but more trapeziform, ventricose or 

 tumid, swollen and projecting at the umboes, usually only one- 

 fourth longer than broad ; the epidermis ranging from dirty yel- 

 lowish-green to olive-brown. Ventral margin neither particularly 

 swollen before the middle, nor peculiarly rising behind. Posterior 

 side abruptly truncated, not projecting below. Lunular region 

 not strictly defined, but flattened at the circumference. Teeth 

 and hinge-margin not peculiar. 



35. N. Bellotii, A. Adams, f. 128. — T. tenuis, subventricosa, 

 cute nitidissima, iu medio olivaceo-virente, lutea autem superne, 

 postice, et aliquando etiam inferne, induta ; nisi ad umbones con- 

 centrice plicato-corrugata. Dimidium auticum oblique semieUip- 

 ticum ; posticum superne subrectangulare, inferne rotundato-sub- 

 angulatum. Latus posticum fere excisum. Margo ventralis 

 integer, in medio subarcuatus, utrinque acclivis. Lunula dense 

 corrugato-phcata, vix defiuita, inferne concaviuscula. Area ex- 

 pansa, aliqnantum subimpressa. — Anterior half obhquely semi- 

 elliptic, posterior half subrectangular above, rotundately broadly 

 subangulated below ; thin, subventricose, with a very highly 

 polished epidermis, which is yellow dorsally, posteriorly, and, for 

 tiie most part, vcntrally, before the middle, and is greenish-olive 



