MALACOZOA. GASTEROPODA. SCUTIBRANCHIATA. 65 



nicating externally by an opening between tbe margin of 

 the body and the mantle ; unisexual. 



Cervicobraiichidta and ChismohrancMata, Blainville. 

 Gastrdpoda Calyptrdcia, and Trachelipoda Neritdcea, 

 Lamarck. Scutibranchidta, Cuvier. SctUu?n, shield ; 

 brdnchice, gills. 



Family I. — Fissurellina. 



Body conical, not spiral; two large triangular, thin 

 tentacula; eyes on slight prominences at their outer 

 margin ; foot large, nearly circular ; branchial cavity 

 opening widely before. Name from the genus Fissurella. 



Genus 1 . Lottia. — Shell conical, with the apex nearer 

 the anterior end, the aperture extremely large, oval 

 or roundish. Gray. 



1. Lottia virghiea. — Shell ovato-elliptical, Uttle ele- 

 vated, subpellucid, with obsolete radiating striae, and co- 

 loured with reddish rays. Named from its beauty and 

 dehcacy. 



Genus 2. Emarginula. — Shell conical, with the sum- 

 mit incHned backward, a vertical notch or slit in the 

 anterior margin. Named from the sUt in the margin. 

 Lamarck. 



1. Emarginida Fissura. — Shell conical, somewhat 

 compressed, cancellated with about forty radiating ribs, 

 and numerous scalar lamellae, the margin crenulate. 

 Fissura, a cleft. 



Genus 3. Rimula. — Shell conical, with the summit 

 inclined backward, and near it a ventrical sht. Ri- 

 mula, a little chink. Defrance. 



1. Rimida Flemingii. — Shell conical, compressed, 

 with twenty-four radiating ribs, alternating with smaller, 

 and cancellated, the margin crenulate. Named after 

 Dr. Fleming. 



F 2 



