UNIVALVES. 



PLATE XXXVIIL 



Genus. POMACEA. 



Character. Shell orbicular, with a small spire of three folds ; mouth open and 

 wide ; umbilicus placed beneath the rim of the mouth ; the edge of the mouth con- 

 tinued all round, and projecting from the body. 



Species. 



No. 1. Pomacea annularis. Shell white, with a brown mouth; the body envi- 

 roned with three stripes of dark brown, richly striped with black ; the rim 

 of the mouth white. A native of the Mediterranean Sea. 



No. 2. Pomacea linearis. Shell pale reddish brown, slightly spotted with pale 

 pink spots ; mouth slightly shaded with a broad band of brown reaching 

 round the body ; the rim yellow. This shell is found on the coasts of North 

 America, and is drawn from a specimen in the Collection of Mr. Stuart. 



No. 3. Pomacea maculata. Shell large, and olive-coloured ; the mouth of a 

 rich brown, streaked and spotted in an elegant manner with dark brown 

 spots ; spire rather acuminate. It is a native of the West Indies. From a 

 shell in the valuable and extensive Museum of Mr. Bullock. 



No 4. Pomacea variegata. Shell red, richly striped in upright and transverse 

 veins of the same colour, the general appearance rather pale ; the mouth 

 white, inclining to brown, the general form very much rounded ; the spire 

 depressed. Native place unknown. 



No. 5. Pomacea orbata. Shell olive-coloured ; mouth of a dark purple, edged 

 with a yellow tint. From a shell in the Collection of Mr. Stutchbury, and 

 supposed to be a native of the West Indies. 



REMARKS. 



The genus Pomacea is here, for the first time, separated from the genus Helix, from the ob- 

 vious difference of the rim, or edge inclosing the mouth, which is continued all round. The 

 Pomacea is one of those shells which are always umbilicate, by a strongly marked hollow 

 ridge or furrow placed on the under part of the body. The difference which distinguishes 

 it from the Turbo is also sufficiently striking, the mouth of the latter being quite circular, 

 and having not so short a spire as the present subject. 



In the Helix genus the rim or edge always stops short upon the body side of the mouth, 

 at the commencement of the umbilicus, as will be perceived by examining the characters 

 of that genus. 



The variety of colours exhibited in the shells of the genus Pomacea atones in some degree 

 for the want of beauty in their forms ; they are frequently covered with an epidermis, which 

 may be removed with considerable advantage by a weak solution of muriatic acid, by that 

 means disclosing the native colours of the species. 



