360 



CRUSTACEA 



Fi^. 568 — Diagram 

 of Mitella (Pilsbry). 

 Explanations as in 

 Fig. 570. 



and Ihla cummingi 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. SCALPELLTTM 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; 

 hemiaphroditic, 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 triangiilar; 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, nil <>f which are fonud 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 



'A, carina. 



