MANGELIA. 461 



B. MANGELIA. 



M. NANA, Loven. 



Pure white, devoid of longitudinal ribs ; very closely sulcated 

 in a spiral direction ; whorls, simply ventricose ; labial sinus 

 very shallow. 



Plate CXII. fig. 8, 9. 



Tritonium namtm, Loven, Index Moll. Scandin. (184G), p. 12. 



Fusus albus, Forbes, Ann. Nat. Hist. (1847), vol. xix. p. 97, pi. 9, f, 3. 



This delicate little shell, which looks not unlike a 

 miniature jP. Islandicus, has a fusiform shape, is some- 

 what glossy, very thin and transparent, and is of an 

 uniform snow-white hue, both externally and internally. 

 The principal turns are most densely encircled with 

 numerous flat costellse, whose intervals are traversed 

 lengthway by most crowded minute raised lines, that are 

 often most apparent beneath the suture (where the riblets 

 are frequently further apart) ; so close are those costellas 

 that to the naked eye, or beneath a low magnifying power, 

 the surface seems merely sulcated, or punctato-sulcated, in 

 a spiral direction. The lines of growth are sometimes 

 coarsely conspicuous upon the spire, which consists of four 

 volutions, that are simply ventricose, or else are slightly 

 more swollen anteriorly, are of moderate longitudinal in- 

 crease, gently taper above, commence with a very blunt 

 mammillary and unsymmetrically coiled apex, and are 

 divided by a fine sutural line. The body, which decidedly 

 exceeds the spire in length (at the least it occupies four- 

 sevenths of the total length), is rather narrow, and though 

 well rounded, is not much swollen ; it gently attenuates 

 anteriorly, with a rather gradual but very convex declina- 

 tion, to a short subcaudal extremity. The mouth, which 

 is devoid of all sculpture, occupies about half the total 



