MALAC0Z0A. GASTEROPODA. NUDIBRANCHIATA. 69 



I. Hdlia Flemingidna. — Shell ob ovate, thin, glossy, 

 white, with faint striae. Named after Dr. Fleming. 



Genus 4. Bullina. — Shell cylindrical, involute, the 

 last turn concealing the rest ; the spire generally sunk : 

 the aperture straight, very narrow, a little widened ante- 

 riorly. Named from Bulla. Ferussac. 



1. Bullina umhilicdta. — Shell oblongo- cylindrical, 

 semitransparent, glossy, with faint growth-lines, the 

 posterior extremity rounded, with a deep and narrow 

 umbilicus. Umbilicatus, having a pit in the spire. 



2. Bullina truncdta. — Shell subcylindrical, thin, semi- 

 transparent, glossy, with distinct shallow sulci on half 

 its length from the posterior extremity, which is truncate, 

 with a wide and shallow umbilicus. Truncdtus, cut off 

 at the end. 



3. Bullina cylindrdcea. — Shell cylindrical, thin, trans- 

 parent, glossy, smooth, or with faint growth-lines, sub- 

 truncate with a deep umbilicus. Cylindrdceus, elon- 

 gated and round. 



ORDER VIII.— GASTEROPODA NUDIBRANCHIATA. 



Respiratory apparatus consisting of branchial tufts 

 or papillae, placed on the back, and exposed. 



Tritonia, Lamarck. Poly branchial a and Cyclobranchi- 

 ata, Blainville. Nudibranchiata, Cuvier. Nudas, bare ; 

 branchia, gills. 



PoLYBRANCHIATA. 



With numerous branchice on the sides of the body. 

 Family I. — iEoLiDiNA. 



Body oval, oblong, or elongated, with papilliform or 

 filamentous branchiae disposed along the sides of the 

 body above ; two pairs of tentacula ; eyes behind the 

 upper. Named from the Genus JEolis. 



Genus 1. tEolis. — Body oblong, tapering to a point, 

 with numerous filamentous or papilliform branchiae in 

 rows on the sides above. Name from JEolus. Cuvier. 



