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 Pijrula 

 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 apertui'e 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 matui'e 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 ratlier 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 



