GENUS — POLLICIPES. 295 



Description. The number of valves in the capituluni 

 has in this genus acquired its maximum. The number 

 varies considerably in the same species, and even on 

 opposite sides of the same individual, and generally in- 

 creases with age. It is more important, that the number 

 of the whorls in P. cornucopia, and in the two following 

 closely-allied forms, also increases with age. In P. sertus 

 and P. sjjinosus, even the number of the whorls varies in 

 different individuals, independently of age. The valves are 

 arranged alternately with those above and below; they 

 are generally thick and strong, making the capituluni 

 somewhat massive ; in some species they are subject to 

 much disintegration ; but in others, the apices of the 

 several valves, especially of the carina and rostrum, are 

 well preserved, and project freely : they are covered with 

 membrane, which, differently from in most species of Scal- 

 pellum, either does not bear any spines, or only exceed- 

 ingly minute points. In all the species there is a sub- 

 rostrum and sub-carina, and often beneath these a second 

 sub-rostrum and sub-carina. In medium-sized specimens 

 there are at least 20 valves in the lowermost whorl. 

 The carina is either straight or curved, but never rec- 

 tangularly bent, and is always of considerable breadth. 

 None of the valves are added to at their upper ends. 

 The scuta have a deep pit for the adductor muscle. The 

 valves lie either some little way apart, or more commonly 

 close together. In P. mitella the scuta and terga are 

 locked together by a fold, and the valves of the lower 

 whorl overlap each other in a peculiar manner, resembling 

 that in which the compartments in the shells of Sessile 

 Cirripedes fold over each other. 



The Peduncle is of considerable length in some of 

 the species, and rather short in others ; it is, in every 

 case, clothed with calcified scales. The scales in the first 

 four species are placed alternately and symmetrically; 

 they are formed and added to in the same manner as 

 in Scalpellum ; they differ in size according to the size 

 of the individual, and consequently the lower scales 



