CLASS GASTROPODA 



To this class belong the snails, 

 limpets, slugs, nudlbranchs (without shells), 

 whelks, and those provided with a more or 

 less spiral shell. All in this class pos- 

 sess a foot, a mantle, and a mantle cavity 

 similar to those of the clam or mussel but 

 assuming quite different characters and 

 habits. 



Three characteristics stand out 

 with prominence: (l) asymmetry, (g) the 

 well-developed and consequently different- 

 ly functioning head, and, (3) the spirally 

 coiled shell which is in one piece. 



The groups into which the Gastropo- 

 da have been divided are based upon the 

 structure of the nervous system, together 

 with the respiratory and sexual organs. 



SUBCLASS PROSOBRANCHIA 



ORDER ARCHAEOGASTROPODA 



Family Acmaeidae 



Shell dish-shaped, conical, apex 

 more or less at one end. The shells may be 

 separated from the Patellidae, a large fam- 

 ily living mostly in tropical seas, by the 

 less distinct border around the aperture, 

 also by the fact that they are never iri- 

 descent. The Acmaeas live upon seaweed or 

 adJiere to rocks often exposed to the surf. 

 Like other sedentary mollusks they are very 

 variable, the shells often being modified 

 to conform to the environment. While a few 

 are from deep water the majority live be- 

 tween high-tide and low-tide marks. There 

 are many more species upon the Pacific than 

 the Atlantic coast of the United States. A 

 radula of Patella is shown in Fig. 28, 

 page 20. 



GENUS ACMAEA Eschscholtz 1830 



ACMAEA CANDEANA Orbigny. Shell gray or 

 buff, depressed, with radiating black lines, 

 often combined with seven to nine broad 

 rays; interior white, brown tinted; wide 

 edged with gray and close set brown lines. 

 Length 1 inch. 



PI. 40, Fig. 15 

 PI. 30, Fig. 14 

 PI. 29, Fig. 1 

 Florida; West Indies 



ACMAEA CANDEANA ANTILLARUM Sowerby. An 

 elevated form, rayed with narrow light blue 

 stripes on a light ground, interior bluish 

 white; body mark deep brown in young shells, 

 covered with white in the adult, border 

 dark and articulated with white. Length 

 20 mm. 



PI. 29, Fig. 2 



Florida Keys; West Indies 



ACMAEA CUBENSIS Reeve. Surface outside 

 with narrow riblets, often obsolete; black 

 lines upon a white ground, also blotched 

 with black; edge of shell smooth. Length 

 £1 mm. 



It probably will be found living or 

 dead upon the Florida Keys and is included 

 here for comparison. 



PI. 29, Fig. 5 



Bahamas; West Indies 



ACMAEA LEUCOPLEURA Gmelin. Shell solid, 

 conic or depressed, apex near center; about 

 twelve strong ribs and twenty to thirty 

 around base; ribs white, spaces between 

 dark brown or black; interior white, bor- 

 dered with black dots, brownish in middle. 

 Length 23 mm. 



This species is more coarsely 

 ribbed than A. cubensis. 



PI. 29, Fig. 13 



South Florida and West Indies 



ACMAEA PUNCTULATA Gmelin. Apex near cen- 

 ter; surface sculptured with low riblets, 

 every third or fourth rib more prominent; 

 delicate pink or yellowish with reddish 

 dots between riblets; epidermis lacking; 

 interior whitish, border narrow and gray 

 in color. Length 1 inch, usually less. 



A very variable shell, the young 

 thinner and presenting quite a different 

 aspect. Florida examples are thinner and 

 narrower than those from the West Indies. 



PI. 29, Fig. 14 



Florida Keys; Bermuda; West Indies; 



Mexico 



74 



