MARINE MOLLUSCA OP THE UNITED STATES. 81 



Genus ARCHITECTONICA, Bolten. 

 Mus. Bolt. 1798. 

 Solarium, Lamarck, Prodr., 74. 1801. 



The species of this genus are fancifully called "stair-case shells" 

 from the appearance of the spiral edges of the whorls in the per- 

 spective umbilicus. Distribution tropical. 



1. A. oranulata, Lamarck. Fig. 150. 



(Solarium.) Anim. 3. Vert., vii. 3. 1822. 

 Shell conoid, yellowish flesh-color, stained with livid-purple, 

 sparingly belted with distant chestnut-red spots and dots ; whorls 

 spirally grooved and granosely warted ; base many crenated ; um- 

 bilicus rather small. 



North Carolina to West Indies. 



Genus LACUNA, Turton. 

 Zool. Journ., iii. 190. 1827. 



The Lacunae feed upon sea-weed, and Love'n observes that when 

 the fuci are of a brown color these animals become green, but if 

 red they assume a rosy tint. They principally inhabit the shores 

 of northern countries, and several species are common to both 

 continents. 



1. L. divaricata, Fabricius. Fig. 151. 



(Turbo.) Fauna Grcenl., 392. 1780. 

 T. vincta Montagu, Test. Brit., 307, t. 20, f. 3. 1803. 

 T. quadrifasciatus, Fleming, Brit. Anim., 299. 1828. 

 L. pertusa, Conrad, Journ. Pnilad. Acad., vi. 266, t. 11, f. 19. 1830. 



Shell small, thin, ovate-conic ; spire pointed ; whorls five, very 



convex, with faint incremental lines; suture deep ; aperture nearly 



circular ; lip sharp and simple ; pillar-lip with a wide and deep 



groove behind, ending in a profound umbilicus ; color yellowish, 



with sometimes four or five dark purplish or reddish bands. 



Length 7.5 mill. 



New England to Neio York. (England.) 



2. L. neritoidea, Gould. Fig. 152. 



Amer. Journ. Science, xxxviii. 197. 1840. 

 ?L. pallidula, Turton (var.), Zool. Journ., iii. 190. 1827. 



Shell small, thin, hemispherical, or obliquely ovate ; whorls 

 three and a half, regularly convex, minutely wrinkled near the 

 suture, and with an occasional transverse scratch, otherwise 

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