21 



inch in place of three in the scrobiculatus. In all the specimens of 

 the latter which have come under my observation, the sides are con- 

 spicuously undulated by a series of distinct waves, in the direction 

 of the lines of growth, which are wholly wanting in umbilicatus. 

 The most obvious distinctive marks then are, in the former, the shi- 

 ning surface and waved sides ; and in the latter, the numerous small 

 flammules, dead surface, and well-marked revolving striae. These 

 revolving striae are plainly indicated on the figure of Lister ; and 

 that they are not merely a style of the engraver's art, but are in- 

 tended to indicate something in nature, may be inferred by comparing 

 the figure with that of N. Pompilius, in immediate proximity, the 

 surface of which is really like that of scrobiculatus. The best of the 

 three specimens examined by me, is now in the possession of Hugh 

 Cuming, Esq., and an inspection of it will fully confirm the above 

 views. 



The synonymy of the two species will then be as follows : — 



N. umbilicatus. Testa suborbicularis, ventricosa, striis confertis 

 volventibus insculpta, utrinque late umbilicata ; marginibus 

 umbilicorum vix rotundatis ; umbilico pervio, infundibuliformi, 

 nigro margine externo vix rotundato ; rufescens, postice radiatim 

 ferrugineo strigata, strigis angustis, confertis. 



N. umbilicatus, Lister, Conch, t. 552. f, 4. 



N. scrobiculatus. Testa suborbicularis, subdepressa, Icevis, ni- 

 tida, lateribus radiatim fluctuatis, utrinque late umbilicata, um- 

 bilico crateriformi, margine externo rotundato, late flavescens, 

 postice radiatim ferrugineo strigata, strigis latis, remotis. 



N. scrobiculatus, Soland. MS. Portland Catal. 169. no. 3653 ; 

 Dillwyn, Catal. i. 339. 



N. Pompilius, var. /3., Gmelin, no. 3369. 



N. crassus umbilicatus, Chemn. Conch, x. t. 137. f. 1274, 1275. 



Le grand Nautile ombilique, Favanne, Conch, i. 726. t. 7. f. B 3, 

 t. 69. f. D 2. 



N. umbilicatus, Knorr, Vergn. iv. pi. 22. f. 4 ; Lamarck, Anim. 

 s. Vert. xi. 322 ; Blainville, Malac. pi. 8. f. 2 ; Crouch, Conch.pl. 20. 

 f. 16; Sowerby, Thes. Conch, pi. 98. f. 7. 



