MAZATLAN UNIVALVES 4A9 
Var. c.=Natica Chemnitzii, Pfr. in Mart. Conch. p. viil.*— 
OC. B. Ad. Pan. Shells, p. 201, no. 295.—‘N. Chemnitz, 
Mhke.” Rve. ms. in Mus. Cum.—(Non N. Chemnitzii, Mke. 
loc. cit. 1849, p. 36.—Nec Recl. Voy. Bon. in B. M. Cat. 
p. an 168 :—=Neverita Chemnitz, H. f A. Ad. Gen. 
i, 208. 
+ Natica Pritchardi, Forbes, Proc. Zool. Soc. 1850, p. 272, 
pl. 11, f2)a-c. 
P+ Natica iostoma, Whe. in Zeit. f. Mal. 1847, p. 178, no. 5. 
Comp. Natica tessellata, Phil. in Zeit. f. Mal. 1848, p. 158, 
moO. 20h (TT aGne oe 8) 
The West-coast shells are extremely variable in size and 
colouring, also in the tumidity of the whirls and elevation of 
the spire. The Mazatlan specimens belong to a small, highly 
coloured variety, which, with the less coloured larger shells, 
was described by Prof. Forbes as N. Pritchardi. On comparing 
these with a series from W. Mexico, collected by Lieut. Freere, 
and another from the Gambia coast collected by Chief Justice 
Rankin, in the Bristol Museum, also with the series from 
various localities in the British Museum and the Cumingian 
Collections, it does not appear that the local types are suf- 
ficiently distinct to be accounted as separate species. The 
Gambia specimens go through the same variations of colour as 
those from W. Mexico. The Mazatlan shells much more closely 
resemble the ordinary Gambia type than the ordinary West 
Mexican type. They are however generally rather flatter in 
the spire, with the subsutural wrinkles rather stronger, and 
the operculum not indented in the inner surface. 
The operculum is thin, shelly, flat or very slightly concave ; 
with a narrow, not prominent, rounded ridge along the outer 
margin, and another small one bounding the part correspond- 
ing to the umbilical callosity. The whole surface is very finely, 
searcely perceptibly, spirally striated: at the base rough and 
callous ; the inner margin thickened, and very scabrous. The 
operculum of the Californian form is rather swollen, smooth, 
glossy, with the outside ridge scarcely seen; the reflex area of 
the callosity scarcely @xcavated, and the inner margin but 
slightly roughened. It differs from the Gulf type, much more 
than this does from the Gambian, ° 
* For justification of the above synonyms, v. the elaborate article of Koch and 
the observations of Dunker. Ifthe W. American shells should prove distinct, 
the name Chemnitzii has precedence over that of Forbes, having been described 
from Mexican specimens, although Menke applies the synonym to African shells. 
