MAZATLAN UNIVALVES 343 
no. 374, p. 438.— Hyd. & Soul. Voy. Bon. pl. 39, f. 6,7:— 
B. M. Cat. p. 34, no. 188. 
Cerithidea Montagnei, Mon. loc. cit. p. 83. 
= Cerithium Reevianum, C. B. Ad. Pan. Shells, no. 205, 
pp. 156, 310. ‘ 
Comp. Cerithium pulchrum, C. B. Ad. loc. cit. no. 204. 
That the Mazatlan shell is identical with C. Reevianum, and 
with D’Orb.’s species, is evident from a comparison of types. 
It is possible that Sow. is right in uniting also the C. pulchrum. 
But in affiliating the China species C. Fortunei, 4. Ad. (Mon. 
l. c. no. 20) and C. Largillierti, Phil. (Zeit. f. Mal. 1848, p. 20, 
no. 83,) the latter as the young of the S. American, he displays 
a judgment only surpassed in singularity by that of Dr. Gray, | 
who calls this species ‘‘only a variety of C. varicosum without 
varices,” (B. MW. Cat. loc. cit.) Kiener’s figure is not charac- 
teristic ; nor was D’ Orb.’s sufficiently accurate for Prof. Adams 
to recognize the species. 
None of the Mazatlan shells are so broad in proportion as 
C. pulchrum, C. B. Ad., nor possess its sculpture. This is stated 
to have 40 ribs on each whirl; Mr. Cuming’s type however has, 
as the spire ascends, about 40, 31 and 26 respectively. It differs 
in its regular varices, 240° distant, and in the spiral striz, one 
of which is conspicuous to the top of the non-decollated spire. 
The continuity of the labrum and labium, by which it is 
further distinguished, depends on age, and is equaled in the 
typical form. Ifa variety, it is a constant one,as Prof. Adams 
found 125 specimens, living with the other species. 
The Mazatlan specimens of C. Montagnei vary considerably 
in the elongation and divergence of the spire, in the number 
and strength of the ribs, and in the amount of spiral sculpture. 
Tn the upper whirls the ribs are comparatively distant, sharp, 
and never tuberculous. On the last whirl they are often very 
close (sometimes with a sudden change,) sometimes nearly 
obsolete, sometimes spirally subnodulous ; varying from 26 to 
about 48. There is always a raised line continuing the suture, 
(very rarely visible in the suture of elongated specimens,) and 
numerous spiral stris round the base. The surface under the 
microscope is often most minutely corrugated ; and the epider- 
mis, whith is thin and deciduous, is spirally striated, or striato- 
corrugated. No varices are ever seen on the spire; and it is 
only a very rare accident if one other is seen besides the 
terminal one. The labrum is widely reflected, often in layers ; 
and in the adult there is always a considerable thickening of 
