MAZATLAN UNIVALVES 259 
Hab.—(Unknown, Sow.) Mazatlan, Menke.—Mazatlan ; com- 
mon, generally coated with black accretion, similar to that 
adhering to Strigilla carnaria, Terebra albocincta, Arca 
“tuberculosa, &c. ; E’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, 6 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. Zool. Soc. 1832, p.201.— Desh. in Lam. An. s. Vert. 
vol. vill. p. 588, no. 40.—Sow. Conch. Til. no. 35, pl. 86, f. 1 :— 
Thes. Conch. p. 530, pl, 116, f. 267-9.—Mke. in Zeit. f. Mal. 
1850, p. 167, no. 20.—C. B. Ad. Pan. Shells, p. 206, no. 307.— 
Rve. Conch. Ic. pl. 23, sp. 101, f. 101, a, 6. 
Vitta picta, H. & A. Ad. Gen. i. 383. 
Comp. N. Guayaquilensis, D’Orb. Sow. Thes. Conch. p. 520, 
no. 44, pl. 114, f. 177.—Rve. Conch. Ic. pl. 23, sp. 104, f. 103 
6. (non a.) 
Comp. N. Fontaineana, B. VM. Cat. D’Ord. 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 denticulation 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 
