MAZATLAN UNIVALVES 259 



Hob. (Unknown, Sow.) Mazatlan, Menke. Mazatlan ; com- 

 mon, generally coated with black accretion, similar to that 

 adhering to Strigilla carnaria, Terebra albocincta, Area 

 tuberculosa, &c. ; L'pool Col. 



Tablet 1200 contains 2 sp. apex sunken. 1201, 5 sp. last 

 whirl swollen, apex appearing. 1202, 5 do. last whirl less 

 swollen. 1203, 5 sp. normal form. 1204, 6 sp. apex more 

 raised. 1205, sp. still more. 1206, 3 do. extremely raised, 

 mouth very slanting. 1207, 5 sp. violet tinge. 1208, 5 separate 

 opercula ; others being in their shells. 



^ 329. NERITINA PICTA, Sow. 



Proc. ZpoL Soc. 1832, p. 201. Desk, in Lam. An. s. Vert. 



vol. viii. p. 588, no. 40. Sow. Conch. III. no. 35, pi. 86, f. 1 : 



Thes. Conch, p. 530, pi, 116, f. 267-9. Mke. in Zeit. f. Mai. 



1850, p. 167, no. 30. C. B. Ad. Pan. Shells, p. 206, no. 307. 



Rve. Condi. Ic. pi. 23, sp. 101, f. 101, a, b. 

 Yitta picta, -BT. Sf A. Ad. Gen. i. 383. 

 Comp. N. Guayaquilensis, D'Orb. Sow. 'Thes. Qonch. p. 520, 



no. 44, pi. 114, f. IW.Rve. Conch. Ic. pi. 23, sp. 104, f. 103 



b. (nona.) 

 Comp. N. Fontaineana, B. M. Cat. D'Orb. Moll. p. 34, 



no. 305. (Rio de Guayaquil.) 



The variations in this species are extraordinary. Not only 

 does it present the changes of colouring recorded below, but 

 the form is very inconstant. Sometimes it is nearly globular, 

 with the spire not exserted and flattened ; sometimes it is 

 much produced. Sometimes the mouth is nearly straight with 

 regard to the axis ; sometimes very slanting. Sometimes the 

 outer lip is regular, sometimes anteriorly lengthened. The 

 brown spot which is supposed to be characteristic of the species 

 varies in intensity, and is scarcely seen in very young shells. 

 It is not uncommon to find specimens whose apex betokens a 

 different painting from that afterwards adopted ; and to find 

 shells whose back affords one pattern and the front another. 

 The denticulatioa also of the inner lip varies in intensity and 

 arrangement ; so that it is difficult to assign any character, by 

 which the whole species may be included and at the same time 

 separated from its neighbours. The operculum is grey outside 

 with an exterior horny layer, and a ridge near the straight 



