148 AMERICAN JOURNAL 



tween adults of S. 'pyrum and S. coronatus ; if young specimens 

 of those species are examined, liOAvever, the differences are found 

 to be comparatively unimportant. It may be remarked that in 

 early youth the shells of all the species of the genus are very 

 similar, all having the -whorls angulated and crenulated, while 

 the whorls themselves are more or less evolved behind the suture. 

 But at an early period a deviation takes place in several types. 



The S. canaUculatiis and its allies continue the normal plan of 

 growth through life, only losing the crenulated margin of the 

 angle, while on the one hand, in S. coronatus and its kindred, 

 the crenulated margin is soon developed into a nodose or dentate 

 one which is continued to maturity ; on the other, in 8. elon- 

 gatus not only is the crenulation of the ridge soon discon- 

 tinued, but the ridge itself becomes obsolete, the whorls at the 

 same time become somewhat more exposed. Finally, in S. fy- 

 rum as in 8. elongatus the crenulations and ridge are soon 

 lost, and the latter is even entirely obliterated in the end, but 

 the whorls in progress of growth encroach more and more on the 

 preceding, so that in the adult the form of Pyrida (Jicus, &c.) is 

 simulated so exactly that the two types can only be distinguished 

 by structural characters, such as the periostraca, channelled 

 suture, plicated columella, sculpture, &c. 



As the name 8ycoty])us of BroAvne is retained for this genus, 

 notwithstanding the claim of it for the genus Pyrula, Lam., an 

 explanation of such course is demanded. 



As Browne's work is accessible to few, his remarks on 8ycoty- 

 pus are here reproduced.* 



" The 8ycotypus or Fig-shell comes next in order, having its 

 aperture in a line with the axis, and terminated in a narrow pro- 

 duced bill like the foregoing ; [Purpura, Browne = 31urices 

 sp.] but it is neither lipped nor toothed, and stretches commonly 

 from a large spiral main. The opening of these shells runs gen- 

 erally about two-thirds of the whole length, and the body, which 

 is roundish and swelling, terminates in a moderately prominent 

 apex. 



" Sycotypus 1. Tenuis substriatus et leviter tuberculatus. 



" The smaller hairy Fig-shell." 



Such is the description of the type which has been identified 

 with Pyrula by Dr. J. E. Gray ! 8ycotypus of Browne has a 

 " narrow produced bill," while Pyrida has a broad patulous one, 

 the one has an aperture about two-thirds of the whole length, 

 while the other has one extending nearly the whole length ; the 

 one is slightly tuberculated or crenulated and "hairy," while 

 the other is unarmed and the mantle being partly reflected over 



* (Browne, Civil and Nat. Hist, of Jamaica, 1756, p. 406.) 



