66 MAIACOZOA. GASTEROPODA. CTCLOBRANCHIATA, 



ORDER v.— GASTEROPODA CYCLOBRANCHIATA. 



Respiratory organs a continuous fringed lamina, sur- 

 rounding the foot. 



PhylUdiai Lamarck. Chismohranchidta and Poly- 

 jildxiphora, Blainville. Cydobranchidfa, Cuvier. Cy- 

 clus, a circle ; hrdiichi(2, 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, elhptical, ovate, or roundish. Linnseus. 



1. Patella vidgdta. — Shell conical, with the apex di- 

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

 ternating with striae, and crossed by striulse, the margin 

 angulate or crenate. Vulgdtus, common. 



2. Patella IfEvis. — SheU 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 yeUo^ish-brown, often 

 rayed with reddish. Lcevis, smooth. 



3. Patella jpelUicida. — 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 striae, yellowish-brown, with some 

 bright blue lines. Pellmidus, 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. — SheU of eight transverse plates, 

 moveable upon each other by muscular bands, Xirwj/, 

 a coat of mail. Linnoeus. 



