MARINE MOLLUSCA OF THE UNITED STATES. 6l 



Genus AMATJROPSIS, Morch. 



1. A. IsLANDiCA, Gmelin. Fig. 104. 

 {Nerita.) Syst. Nat. 3675, 1790. 



Natica helicoides, Johnston, Trans. Berw. Club, i. 69, 266. 1835. 

 Natica canaltculata, Gould, Am. Journ. Sci., xxxviii. 197. 1840. 



Shell subglobose, rather ponderous, dingy-white, nearly smooth 

 and somewhat gloss}', covered with a dark gamboge-colored epi- 

 dermis ; whorls four, the upper portion of each turning before it 

 joins the preceding whorl, so as to form a broad, shallow canal at 

 the suture, and giving the spire a turreted appearance ; aperture 

 about two-thirds the length of the shell, nearly semicircular ; lip 

 sharp, a little spreading in front, the inner margin nearly a straight 

 line, and overspread with a thick callus ; interior white ; umbilical 

 opening a mere slit," generally none. 



Length 2*7.5, diam. 18 mill. 



Resembles in shape Paludina ponderosa. 



Massachusetti northwards {Eur.). 



Genus SIGAKETUS, Lamarck. . 

 Prodr. 77. 1799. 

 H. and A. Adams, and others, use the generic name Catinits, 

 Klein, in preference to that given b}- Lamarck, but Klein's genus 

 is named ^^Catinus lactis,^' and is, therefore, not admissible. 



1. C. PERSPECTivus, Say. Fig. 105. 



Am. Conch., iii. t. 25. 1831. 



Shell ovate, elongate, depressed. Surface with numerous im- 

 pressed, transverse, slightly undulated lines, crossed bj'revolving 

 striae which become obsolete beneath. Aperture more than three- 

 fourths the entire area of the shell. Whorls three; spire de- 

 pressed, smooth ; suture distinct, but not deeply impressed. 

 Milk-white, sometimes tinged with brown ; within smooth and 

 polished, and faintly iridescent. 



Length 37, of aperture 24 mill. 



New York, souihteards. 



2. C. MACULATUS, Say. Fig. 106. 



Am. Conch., iii. t. 25. 1831. 

 Shell with numerous transverse hardly undulated impressed 

 lines and longitudinal wrinkles; spire scarcely prominent, slightly 

 convex; whorls about three; suture a simple impressed lino. 



