66 MALACOZOA. GASTEROPODA. CYCLOBRANCHIATA. 



ORDER V. GASTEROPODA CYCLOBRANCHIATA. 



Respiratory organs a continuous fringed lamina, sur- 

 rounding the foot. 



PhyUidia y Lamarck. Chismobranchidta and Poly- 

 pldxiphora, BlainviHe. Cyclobranchidta, Cuvier. Cy- 

 clus, a circle ; brdnchice y gills. 



FAMILY I. PATELLINA. 



Body convex, covered by a conical shell, having the 

 apex nearer the anterior end. Named from the Genus 

 Patella. 



GENUS 1. PATELLA. Shell conical, with the aperture 

 extremely large, elliptical, ovate, or roundish. Linnaeus. 



1. Patella vulgdta. Shell conical, with the apex di- 

 rect, the surface radiated with about eighteen ribs, al- 

 ternating with strise, and crossed by striulae, the margin 

 angulate or crenate. Vulgdtus, common. 



2. Patella Icevis. Shell moderately thick, horny, 

 with the apex obtuse, much nearer the anterior end, the 

 surface concentrically striate, and usually marked with 

 strong growth-lines, the colour yellowish-brown, often 

 rayed with reddish. Lcevis, smooth. 



3. Patella pellucida. Shell thin, fragile, transpa- 

 rent, with the apex incurved, obtuse, close to the 

 smaller end, the surface with about twenty-eight faint 

 ribs, and intermediate strise, yellowish-brown, with some 

 bright blue lines. Pellucidus, nearly transparent/ 



FAMILY II. CHITONINA. 



Body elliptical, depressed, or little convex, covered 

 by a shell composed of generally eight pieces. Name 

 from one of the genera. 



GENUS 1. CHITON. Shell of eight transverse plates, 

 moveable upon each other by muscular bands. Xtr<j>, 

 a coat of mail. Linnaeus. 



