and Pyrula (Fulgur) perversa. 29 
marck) is not a distinct species from P. carica (Lamarck), but 
simply a reversed form of that shell. 
The chief distinctions relied on for the discrimination of the 
two species, independently of the difference in the direction of 
the whorls, are 
1. The comparatively greater breadth of the shell in Pyrula 
carica. 
2. The orange-red colouring of the columella in the same 
species. 
Now let us see how far these distinctions are worthy of 
reliance. 
1. On measuring a number of both shells, I find that in 
shells of either species in which the length is equal, the breadth 
is also equal. 
2. As to colouring: in specimens of P. carica, in this museum 
and other collections which I have examined, the colour of the 
columella varies from the typical deep orange, through various 
shades of yellow more or less intense, to, in one instance, a pure 
white—this individual being young, but not very small. Again, 
in specimens of P. perversa, I find that the colouring of the 
columella varies from the normal white to a yellow, in some 
instances deeper than that of many specimens of P. carica. _ 
Another distinction sometimes relied on is, that the interior 
of the aperture in P. carica is merely striated, whereas in P. 
perversa it is grooved; but here, again, this appears to be an 
individual character, depending more on age than anything else; 
for the aperture of young specimens of P. carica is distinctly 
grooved; and the grooves in the aperture of mature individuals 
of P. perversa become in most instances almost obliterated, 
degenerating into mere striations. 
_ The characters of the two species based on the form of the 
spire and the external coloration and sculpture of the shell are 
so variable that they must, I think, be regarded rather as 
individual than specific. 
There is one obstacle, however, to the admission of the spe- 
cific identity of the two forms—namely, the difference of locality, 
P. carica being usually considered to be confined to the more 
northern seaboard of America, and P. perversa to the more 
southern. This fact might seem to take the case out of the ordi- 
nary one of reversed shells ; nevertheless a parallel case might, 
I think, be found in the differences caused by locality in Pur- 
pura lapillus, Buccinum undatum, &c. The fact itself, moreover, 
In the case under consideration requires confirmation ; and it is 
by no means certain that P. perversa and P. carica are not both 
found in the West Indies. There is, indeed, in the collection 
