BURSA. 105 



they have been termed mask-shells ; they are not numerons 

 in species, and inhabit sandy mud in rather deep water. 



Species of Distorsio. 



anus, Linn. decipiens, Reeve. 



cancellina, Desh. reticulata, Linn. 



constricta, Brod. ridens, Reeve. 



Genus BURSA, Bolten. 



Shell ovate or oblong, compressed, with two rows of 

 continuous varices, one on each side ; aperture oval ; colu- 

 mella arcuated, and ridged or crenulated ; canal short, re- 

 cuvred ; outer lip crenated. 



Syn. Ranella, Ijam. Gyrineum, Link. Bufo, Montf. 

 Biplex, Perry. Rana, Humph. Bufonaria, Sckum. 



Ex. B. rana, Linnceus, pi. 11, fig. 3 ; Operculum, B. 

 pusilla, Broderip, fig. 8, a, 8, h. Shell, B. rana, fig. 3, c. 



The species of Bursa are mostly tropical, the majority 

 being from the Eastern seas ; they are found, when varie- 

 gated and with nodose armature, in rocky places and on 

 coral reefs ; the winged species, with a smoother surface, 

 are from deep water. They move about with considerable 

 animation, and crawl rapidly. 



Species of Bursa. 



albifasciata, Sow. niargaritula, Desk. 



bufonia, i>o/^ nana, /SW. 



crassa, Desh. nobilis, Reeve. 



crumena, Lam. rana, Li^m. 



elegans, Beck. Suesonii, March. 



foliata. Brad. subgranosa. Beck. 



VOL. 1. P 



