Calyptraeidae 129 



Several living X. conchy liophora kept in an aquarium, affixed 

 only left valves of Chione cancellata to their shells, although other 

 bivalve shells and bits of gravel were available. Additions to the 

 defensive armor were made at night, suggesting that the species 

 may be nocturnal in habit. 



Livmg specimens dredged in three to six fathoms on gravelly 

 bottom about reefs. 



Family CALYPTKAELDAE 



Distribution of members of this family is common to all seas, 

 from shallow water to considerable depths. 



The mollusks are sedentary and adhere tenaciously to the sur- 

 faces of rocks or shells where they become accidentally located in 

 the early stages of their growth. That portion of shell or stone 

 immediately beneath the foot of the animal often becomes dissolved 

 or worn away, leaving an oval depression. 



Genus CALYPTRAEA Lamarck, 1799 

 Calyptraea centralis-^s Conrad PI. 24, figs. 171a, b 



Alt., 2; diam. of base, 5.5 mm. Shell thin, conic, cap-shaped; 

 white, with transparent epidermis; apex sharp, excentric, spiral, 

 tilted from vertical, nuclear whorls glassy; sculpture of growth 

 lines concentric to round base; sometimes fine radial striations from 

 apex to base; basal aperture round, margin sharp; interior polished; 

 thin spiral septum from base to apex; mollusks adherent to other 

 shells. 



In depths of one to more than fifty fathoms. 



Triangular capsules covered by front part of parent's shell until they 

 hatch in crawling stage. Capsules fixed in a bunch by their narrow ends 

 to a stone or shell. They are transparent, colourless, 3 to 3^ mm. long, 

 12 to 25 ova in each capsule, floating in intra-capsular fluid. Eggs are 

 usually concentrated at broad end of the capsule — Marie Lebour. 



Genus CRUCIBULUM Schumacher. 1817 

 Cmcibnlum striatum^-a (Say) PI. 24, fig. 172 



Alt., 12; diam. of base, 25 mm. Shell conic, cap-shaped; apex 

 laterally excentric, beaked; anterior declivity of shell convex, pos- 



228 Gr., kalyptra, covering for the head; Lat., centralis, center. 



229 Lat., crucibulum, an earthen pot; striatum, striped. 



