478 MAZATLAN UNIVALVES 
Whether or not the Pacific specimens of the hemastomoid 
type are distinct from the Atlantic, is not yet agreed upon by 
naturalists. That the Mazatlan specimens are conspecific, I 
cannot doubt after a careful scrutiny of more than 500 speci- 
mens. Whether the Lamarckian P. bicostalis be the West 
American shell, as supposed by Reeve, or the E. Indian, as 
decided by Blainville, cannot be determined by his diagnosis. 
But as the W. coast shells were scarcely known in Lamarck’s 
days (except those brought by Humboldt & Bonpland, which 
are specified as such,) when there is a doubt, it seems fair to 
give the benefit of it to the old East and West Indian species. 
Supposing the local forms to be distinct, it is proposed to 
retain Blainville’s name for the W. American shells; leaving 
the P. bicostalis for the E. Indian, P. hemastoma for the 
European, and P. Floridana for the W. Indian types. The 
P. undata of Lam. is almost certainly the W. Indian species 
(not hemastomoid) well figured (among others) by Kiener. 
This does not occur on the West Coast. The Mazatlan shells 
are either (1) very depressed, like P. deltoidea, thick, of a 
uniform gray colour, with distant coarse spiral strie, stout 
tubercles, and wholly orange mouth, (P. consul of Menke not 
Lam.) : or (2) almost wholly assuming the usual appearance 
of P. hemastoma: or (3) of a Buccinoid shape, with very faint 
tubercles, richly variegated brownish colour, shewing at the 
mouth, and comparatively thin texture, (P. undata of Val. not 
Lam.) : or (4) of the same shape, with stout tubercles, and 
back richly coloured, as described by Reeve under P. bicostalis. 
Rarely the shell is almost wholly of a reddish brown. When 
painted, the pattern is extremely various, being laid on some- 
times in irregular patches, sometimes in variegated threads 
between the spiral strie. These vary in width and depth, but 
are never so close as in the specimens observed from the 
Atlantic. Mr. Hanley has also pointed out that the strie are 
punctured; an appearance due to the intersection of faint 
strie of growth, which follow the crenated form of the mouth, 
and often are but faintly discernible in the coarsely grooved 
consuloid specimens. The mouth is often nearly smooth and 
white within, till near the labrum, where orange develops, 
with spiral ridges sometimes displaying an inner row of tuber- 
cles. But sometimes (especially when young,) it is deeply 
lirate over the whole surface, which is brown, while the swollen 
ribs are light yellow. The labium has always more or less of 
an orange deposit, wrinkled near the base, and with an infra- 
sutural rib. There are five smooth apical whirls, sometimes 
