48 NUCULTD^. 



The surface, on the removal of the epidermis, appears faintly ra- 

 diatingly striated, and the teeth, in the adult, are about twenty- 

 two on one side and eleven on the other ; these strife are much 

 more manifest in the fry, which are provided, as usual, with a 

 much smaller number of teeth. All the specimens I have seen 

 named " radiafa, Dekay," appear to be the young of this species, 

 but the furrow represented in his figure I have never descried (ex- 

 cept as an accident of growth) in any Nucnla. 



9. N. PAULLULA, A. Adamx, f. 131, 132. — T. minuta, perob- 

 liqua, subovata, longitudine latitudinera paululum superante, valde 

 inaequilateralis, veiitricosa, cute palhde olivacea induta, undique 

 sublsevigata. Extremitas lateris antici producti subattenuati ro- 

 tundata ; latus ])OPticum, acclivitate obliqua marginis ventralis 

 crenati et arcuati, inferne rotundato-excisum. — Ifiiiute, very ob- 

 lique, subovate, not quite so broad as long, ventricose, mode- 

 rately strong, very inequilateral, with a polished pale olive-coloured 

 epidermis, everywhere smoothish, yet with irregular concentric 

 incremental sulci : extremity of the produced and tapering an- 

 terior side rounded. Ventral margin crenated within, arched, 

 rising behind so as to obliquely round off' the posterior corner. — 

 The same poor specimen has served ]\Ir. Adams and myself for 

 description, and no definite characters can be derived from it. Its 

 beaks are eroded, but apparently much reflected : the lunular area 

 is not either decidedly prominent or clearly defined. 



10. N. MiTRALis, Hhuls, f. 144. — T. conoidalis, valida, ventri- 

 cosa (in exeraplis adultis), Itevis, cute nitidissima flavfi induta, 

 valde infequilateralis. Extremitas antica rotundato-subcunei- 

 formis ; postica inferne rotundato-excisa. Nates peracutae, in- 

 voluta?, eminentes. Area tubercuhs transversim costellata. Lu- 

 nula baud prominens, concave definita. Cartilage pcrobliqua. — 

 Longitudinally coiioidal, ventricose when adult, with a polished 

 olivaceous-yellow epidermis, smooth. Anterior side greatly pro- 

 duced, its extremity rotundately subcuneiform ; ventral margin 

 arched, crenated, and rising behind so as to obliquely round off" the 

 corner of the very short and nearly straight posterior side. Beaks 

 very acute, prominent, involute, not touching. Front dorsal region 

 barred across by short costellar tubercles that do not extend far 

 from the but little curved margin. Lunular region excavately 

 defined, not prominent : cartilage very oblique. — The typical form 

 of mitraUs is rather sharper at the beaks and more slender at the 

 anterior tip than in the more swollen gibba. 



11. N. MARMOREA, Hindg, f. 14.5. — "T. elliptica, solidula, al- 



