MANUAL OF NATURAL HISTORY. 303 



nula denticwlata of Say, on the King-crab. Some 

 of the pedunculated genera form grooves in stones 

 and shells, as Conchotrya of Gray, and Lithotrya 

 of Sowerby ; others are found attached in bunches 

 to floating objects, as Lepas anatifera, Linn. ; while 

 others again, as the Alepas parasita of Lesson, are 

 found parasitic on Medusae and A. minuta of Rang, 

 on the spines of the Cidaris or Turban-Urchin. 

 The curious genus, Alcippe of Hancock, is truly a 

 burrowing Cirrhopod, perforating the substance of 

 shells, and entirely concealing itself in chambers of 

 its own formation, which are lined with a calcareous 

 deposit ; the exact mode in which this naked ani- 

 mal, totally unprovided with shelly plates, forms the 

 excavations in which it lives, has not yet been as- 

 certained. 



V. CLASS. — Cirrhopods (Cirrhopoda). 



Animal soft, symmetrical, covered with a fleshy 

 mantle, and fixed in a multivalve shell ; body re- 

 versed, ending in a tail somewhat jointed and furn- 

 ished with long, horny, articulated cirrhi subservient 

 to respiration ; mouth with mandibles and maxillae ; 

 sexes united. In the young state swim freely about. 



I. ORDER. — Pedunculate-Cirrhopods (Pedunculata). 



Body supported on a coriaceous, hollow, contrac- 

 tile peduncle, fixed to submarine bodies, and usually 

 protected by five shelly valves disposed in two la- 

 teral plates, with a medial narrow piece behind. 

 1. Family. — Barnacles -proper (Lepadidae). Pe- 



