360 



CRUSTACEA 



Fig. 568 Diagram 

 of Mitella (Pilsbry). 

 Explanations as in 

 Fig. 570. 



and Ibla cummin gi in the Philippines, however, being unisexual with com- 

 plementary males, and Scalpellum vulgare of the European seas hermaph- 

 rodite also with complementary males; Lithotrya 

 bores into rocks and mollusk shells and coral: 

 about 10 species. 



1. MITELLA Oken (Pollicipes Leach) (Fig. 568). 

 Shell consists of from 18 to over 100 pieces, of which 

 the carina, the terga, and the scuta are the largest; 

 hermaphroditic: 8 species. 



M. polymerus (Sowerby). Shell composed of 

 upwards of 180 pieces arranged in several whorls, 

 decreasing in size from above downwards; total length 

 7 cm.: west coast of America; common. 



2. SCALPELLUM Leach (Fig. 569). Stalk thick, short, 

 and usually scaly; shell composed of 12 to 15 pieces; 

 either unisexual or hermaphroditic, with complementary 

 males: 140 species; mostly in deep water. 



S. stroemi Sars. Stalk about half as long as body 

 and covered with imbricated scales; total length 12 mm.: 

 in deep water in the gulf of Maine, and to the northward ; 

 Europe. 



FAMILY 2. LEPADIDAE. 



Fig. 569 



Diagram of 



Scalpellum 



(Pilsbry). 



Explanations as 



in Fig. 570. 



Stalk much narrower than the rest of the body and without scales; 



body flattened and usually covered with a shell consisting of 5 pieces, 

 a pair of large scuta at the stalk end of the body, a 

 pair of smaller terga at the opposite end and a 

 median dorsal carina which lies along the hinge, the 

 shell opening and the legs protruding on the ventral 

 side; Anelasma, which lives parasitically in the skin 

 of dogfish in the North Sea, is without a shell; 

 hermaphroditic, without complementary males : about 

 7 genera and 30 species, which attach themselves 

 usually to floating objects. 



1. LEPAS L. Goose barnacles (Fig. 570). 

 Scuta broad and triangular; terga and carina well 

 developed, the latter reaching posteriorly between 

 the former and all 5 parts of the shell abutting on 



one another : about 6 species, 5 American, all of which are found on both 



coasts. 



L. fascicularis Ellis and Solander. Stalk short, not as long as the 



body; plates thin and paper-like; carina bent at right angles; length 



Fig. 570 

 Lepas anatifera 



(Pilsbry). 



1, scutum ; 2, tergum 

 3, carina. 



