160 nuchlim;. 



olivaceo-lutescente vel cinerascente induta, intus argentea. Margo 

 dorsalis antice convexus, declivis ; ventralis arcuatus, integer, 

 postice baud sinuatus, et ibi conspicue acclivis, cum margine 

 postico rectiusculo anguluui valde obtusurn formans. Nates 

 parvre, acuta?, haud prorainentes. Lunula magna, concentrice 

 subrugosa, planulata, angulo definita. Area inconspicua. — Far. 

 Extremitas antica tantum rotundata ; postica aliquantum promi- 

 nens magisque angulata. — Very oblique, truncated-elliptic, strong, 

 subventricose, smooth, with a pale-yellowish or ashy-olive shining 

 epidermis. Anterior side tapering from above to a rounded ex- 

 tremity ; its convex dorsal edge at first but little, subsequently 

 decidedly sloping. Posterior margin almost perpendicular, form- 

 ing a very obtuse angle with the arcuated and entire ventral edge, 

 which rises without sinuation, more peculiarly behind. Beaks 

 small, acute, not projecting. Lunule large, more or less wrinkled 

 concentrically, angular at its circumference from its flatness. No 

 marked escutcheon. Hinge-margin, teeth, and cartilage not re- 

 markable. Nacre silvery-white. — Far. Anterior end well rounded, 

 not tapering from above only : posterior end more angulately pro- 

 minent. — This may possibly be the obliqua of the ' Voyage de la 

 Venus/ 



30. N. Layardi, A. Adams, f. 153. — T. N. convexa valde as- 

 similis, tenuis, autem, minus ventricosa, tantum obsolete, remo- 

 tiusque, corrugata; lunula majore subangulatim circumcincta. 

 Cutis nitidissima, cinereo-virens. Margo ventralis haud postice 

 sinuatus. Nates haud prominentes. Cartilago haud horizontalis. 

 Superficies interna albo-margaritacea. Dentes circiter 15-6. — 

 Closely resembling convexa, but decidedly thin, less ventricose, 

 only faintly (rather remotely) wrinkled concentrically ; the lunule 

 rather larger, subangulately defined. Epidermis polished, greenish 

 ash-coloured : ventral margin not indented near the hinder end. 

 Umboes not prominent. Cartilage not horizontal : nacre white ; 

 teeth about fifteen and six, sharp, vaulted, moderately high. 



31. N. jEgeensis, Fortes, f. 154. — "T. ovata, subdepressa, 

 laevi, ina'quilaterali, antice rotundata, postice angulata, marginibus 

 internis lsevibus." — A single valve (the only specimen now at- 

 tainable) was given to the author by Professor Forbes, and from 

 it can only be gleaned as an addition to his most inadequate de- 

 scription, that the shell is subventricose at the umboes, the epi- 

 dermis of a polished oil-yellow, the dorsal areas wholly unsculp- 

 tured, the lunule concavely defined, the beaks very prominent, 

 and the ventral margin much arcuated. For other details of shape 



