362 CRUSTACEA 



with longitudinal ridges; length up to 5 cm.: North Atlantic coast, 

 extremely common between tide lines. 



B. eburneus Gould. Ivory barnacle. Shell low and broad in form 

 and with a smooth, white exterior; base of shell calcareous: common 

 from Massachusetts Bay to the West Indies, chiefly below low-water 

 mark; often in brackish and even fresh water. 



B. crenatus Bruguiere. Shell white, up to 34 mm. high and 19 mm. 

 wide; base calcareous and very thin: Atlantic coast, on stones and 

 shells in deeper water, also on ships. 



B. tintinnabulum (L.). Shell often ribbed longitudinally, reddish 

 or bluish in color with a calcareous base; up to 6 cm. in diameter and 

 in length: cosmopolitan, in the warmer seas, often brought to our coast 

 on the bottoms of vessels; is eaten in many countries. 



FAMILY 4. CORONULIDAE. 



Similar to the preceding family but differing in that the terga and 

 scuta, although freely movable, are not hinged with one another; base 

 of shell membranous: on Cetacea; 4 genera and 7 species. 



CORONULA Lamarck. Shell formed of 6 principal pieces and wider 

 than high; terga and scuta much smaller than the opening: 3 species, 

 on whales. 



C. diadema L. Shell crown-shaped, scuta present, terga very small 

 or wanting: off the New England coast. 



SUBORDER 2. ABDOMINALIA. 



Body segmented, surrounded by a voluminous mantle but without 

 a shell, and with only 3 pairs of feet on the hinder part of the thorax; 

 unisexual; the animal bores into the shells of mollusks and cirripeds: 2 



families. 



FAMILY ALCIPPIDAE. 



Stalk weak and with a large chitinous disc of attachment; legs 

 uniramose; mantle opens on the side; males minute, without legs, 

 attached to the females: 1 genus. 



ALCIPPE Hancock. With the above-mentioned characters : 1 species. 



A. lampas Hancock. Length 6 mm.; bores in dead Natica shells 

 which are inhabited by hermit crabs: Woods Hole. 



SUBORDER 3. RHIZOCEPHALA. 



Body without segmentation, appendages, or shell and sac-shaped, with 

 a stalk composed of branched thread-like projections which extend into 

 the body of the host; without intestine; hermaphroditic, with comple- 



