MA1ACOZOA. GASTEROPODA. SCUTIBBANCHIATA. 65 



nicating externally by an opening between the margin of 

 the body and the mantle ; unisexual. 



Cervicobranchidta and Chismobranchidta, Blainville. 

 Gastropoda Calyptrdcia, and Trachelipoda Neritdcea, 

 Lamarck. Scutibranchidta, Cuvier. Scutum, 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 virginea. Shell ovato-elliptical, little ele- 

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

 loured with reddish rays. Named from its beauty and 

 delicacy, 



GENUS 2. EMARGINULA. Shell conical, with the sum- 

 mit inclined backward, a vertical notch or slit in the 

 anterior margin. Named from the slit in the margin. 

 Lamarck. 



1. Emarginula Fissura. Shell conical, somewhat 

 compressed, cancellated with about forty radiating ribs, 

 and numerous scalar lamellse, the margin crenulate. 

 Fitsura, a cleft. 



GENUS 3. RIMULA. Shell conical, with the summit 

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

 mula, a little chink. Defrance. 



1. Rimula Flemingii. Shell conical, compressed, 

 with twenty-four radiating ribs, alternating with smaller, 

 and cancellated, the margin crenulate. Named after 

 Dr. Fleming. 



F 2 



