184 



to the right below and reflected to the left. Umbilicus, deep and 

 narrow. Lahral lamella, widely spreadiug. Operculum, ? 



Height 0-059, greatest breadth 0-087, least breadth 0-069. 



Named in complimeut to Robert Swift, Esq., of the Island of St. 

 Thomas, an ardent coUector. 



Genus VI. Petitia, Chitty. 

 Shell, globose discoid. 



Petitia Petitiana, Chitty. See Stoastoma Petitianum, Ad. 

 Ann. Lyc. New York, v. n. 2. p. 67 ; Contr. Conch. p. 151 ; Cat. 

 Phan. p. 232. 



Hab. Peace River, Manchester. 



Petitia Cumingiana, Chitty. See Stoastoma Cumingianum, 

 Ad. Mon. Stoast. Ad. 1849, p. 9 ; Cat. Phan. p. 231. 



Hab. ? Manchester. 



Note. — If I have the right type of this shell, the operculum, in 

 addition to the "numerous lamellar grains" deseribed by Adams, 

 has 6 or 7 very slightly raised vertical lamellse curving from above 

 to the left below, with aninner raised margin iuclosingthe eoncavity 

 and sloping outwards to the extreme edge of the operculum. — 

 Chitty. 



Petitia Anthoniana, Chitty. See Stoastoma Anthonianum, 

 Ad. Contr. Conch. p. 151 ; Cat. Phan. p. 232. 



Hab. ? Manchester. 



Petitia Stevensiana, Chitty. 



Hab. Yallahs Hill. 



Form, globose discoid. Colour, very light brown. Sculpture, 23 

 well-raised ineąuidistant spirai carinse, wider apart below round the 

 umbilicus ; on the upper whorls 7- Spire, slightly elevated, with 

 convex outlines. TFhorls, 4, well rounded, with a deep suture. 

 Aperture, subelliptical, well detached from the body-whorl ; slightly 

 constricted and scarcely expanded, and but little defiected below. 

 Labrum, double, outer edge very finely pectinated by the spirai 

 carinse ; inner edge white, smooth, slightly thickened and reflected ; 

 contiuuous with the labium above, vrith a slight curve. Labium, 

 almost straight, very slightly curved to the right below, where it is 

 below the plane of the labrum. Umbilicus, deep. Labral lamella, 

 produced to a saw-like tooth at some little distance below its junc- 

 tion with the labium ; convex extemally. Operculum, ? 



Height 0047, greatest breadth 0086, least breadth 0-065. 



Named in compliment to the naturalist's universal friend, S. Ste- 

 vens, Esq., Bloomsbury Street, Loudon. 



