IV 



PKDUXCULATA POLUCIPKS AM) SCAI.PELLl '.]/ 85 



istic of numerous skeletal plates, the peduncle being frequently 

 covered with small calcareous pieces, which graduate into the 

 larger more regularly placed scutes on the capitulum (Fig. 54). 

 The species of this genus, many of which 

 are among the largest Cirripedes, are widely 

 distributed in the temperate and tropical 

 seas, living for the most part attached to 

 rocks and often in deep water. P. cornu- 

 occurs off the Enlish and Scottish 



coasts. 



The members of the genus Scalpellum, 

 which is represented by exceedingly numer- 

 ous species in the Cretaceous period, also 

 possess a large number of plates on the 

 capitulum, and often on the peduncle as 

 well, but never so many as in Pollicipes. 

 Although the arrangement of the plates 

 varies much in the different species, we may 



,. , . c , FIG. 54. PoUicitirs witclla, 



describe a i airly typical case, that ol the x L (After Darwin.) 

 common ^n//j'/ ////,/ Tide/are (Fig. 55, B). 



The valves of the capitulum are held together by the median 

 dorsal piece called the "carina"; the other unpaired skeletal 

 piece is the "rostrum," in front, just, beluw the place where the 

 valves c u'ape to allow the pn>t rusion of the limbs. The paired 

 pieces receive the names "scutum," 'termini," and '' laterals," 

 and the peduncle is covered with rows of small plates. 



The genus 8ca/jn'//tnn is a, very laiye one, and is widely 

 distributed, though at the time at which Dar\\in wrote only six 

 species \\ere known. The reason I'm- this is to be found in the 

 fact, that the ^reat, majority of the species live at greal depths. 

 so that they remained unknown until the expeditions of the 

 Challenger and other deep-sea expeditions brought them to livdit. 

 They may al'lix themselves, generally in considerable numbers 

 together, on branching organisms, such as ('orals, Polyzoa, and 

 Hydroids, but often also on empty shell.-, rocks, ami other foreign 

 bodies. The body is colourless or of a pale llesh colour, but 

 a colony of these animals, expanded and drooping in various 

 altitudes from a, piece of coral, gives the appearance of some 

 graceful exot ie (lower. 



Perhaps the most interesting feature of the -enus is the 



