176 MALACOZOA. GASTEROPODA. SCUTIBRANCHIATA. 



ORDER III. GASTEROPODA TUBULIBRANCHIATA. 



No species of this order have been met with in our 

 seas. 



ORDER IV. GASTEROPODA SCUTIBRANCHIATA. 



Respiratory apparatus a cavity on the back, contain- 

 ing pectinate or filamentous branchiae attached to its 

 roof, and communicating externally by an opening 

 between the margin of the mantle and the body, either 

 on the back or to the left. 



FAMILY I. FISSURELLINA. 



Animal with the body conical, not spiral; the head 

 broad, depressed ; the tentacula two, large, triangular, 

 thin ; the eyes situated on a slight projection of the 

 middle of their outer margin ; the mantle very thin ; 

 the foot large, nearly circular; the branchial cavity 

 opening widely before, and containing filamentous 

 branchiae. 



Shell conical, with the summit direct, or curved. 



The species are all marine, and occur chiefly in warm 

 climates. Three only have been found in our district. 



GENUS 1. LOTTIA. 



Animal elliptical or roundish, convex, covered by a 

 univalve conical shell ; head with two tapering tenta- 

 cula, bearing the eyes near their base externally ; mouth 

 fleshy, with a short proboscis, and containing a lingual 

 denticulate filament ; foot very large, elliptical or 

 roundish; mantle marginate, with an inner circle of 

 filaments between it and the foot ; respiratory cavity 

 containing a vascular elongated scaliform or pectinate 

 branchia. 



Shell conical, with the apex nearer the anterior end ; 

 the aperture extremely large, elliptical, oval or roundish. 



