464 PELORIDJ5. 



Authors state that Natica has affinity with Sigaretus, an 

 exotic genus of which there is no true British species. We 

 cannot concur in this view until the anatomy of the latter is 

 more fully examined : if it be found to have the retractile pro- 

 boscis, it will be in the same category as Natica, and must be 

 withdrawn from the Haliotida. 



N. MONILIFERA, Lamarck. 



N. monilifera, Brit. Moll. iii. p. 326, pi. 100. f. 1 ; (animal) pi. P.P. 



f. 6, as N. canrena. 

 N. glaucina, Auct. 



Animal inhabiting a spiral, globosely conical, smooth shell of 

 6-8 tumid volutions. The mantle, neck and body are of the 

 palest or lightest mouse-colour ; the mantle is thin, rather lax, 

 but does not extend beyond the shell. Lamarck's commentator, 

 M. Deshayes, says, "Le manteau se developpe particuliere- 

 ment sur les parties anterieures de la coquille :" this is quite 

 incorrect; he has mistaken the upper skin of the anterior 

 portion of the foot, which some call the mentum, for the 

 mantle. There is no distinct head ; the only vestige of one 

 is a compressed arcuated veil which is fixed by the centre of 

 its membrane on the anterior part of the fleshy tunic of the 

 proboscidal sheath, and on each side by a small white muscle 

 to the base of the groove formed by the neck and skin of the 

 foot, at the centre of which, and under the veil between it 

 and the inside of the front skin of the foot, the yellowish- 

 white proboscis and the end of its inner cylinder may be seen 

 retracted; the head- veil is shallow, sinuous, or lunated, 

 breaking at the right and left sides, very far apart, into two 

 moderately long, flat, triangular, pointed tentacula, red-brown 

 on the upper and outside half, and white on the lower and 

 inside portion, forming at the extreme angles small subcircular 

 auricles. The eyes in this species are so excessively minute 

 as scarcely to be detected ; however, if they really exist, we 

 know their precise position by those of N. nitida, in which 

 they are very visible and immersed in the skin at the centre of 

 the anterior base of the tentacula, on the white concealed 

 portion, but being always covered, they appear to be of little 



