154 



ANNULOSA. 



with intersecting rows of plates, as in Loricula. These plates, 

 when detached and occurring in an isolated condition, might 

 very readily be mistaken for the shells of Pteropods. The 

 genus is known both from the Wenlock Limestone of Dudley 

 and the Ludlow Rocks of the Pentland Hills near Edin- 

 burgh. The Devonian, Carboniferous, and Permian forma- 

 tions have as yet yielded no certain traces of Pedunculated 

 Cirripedes, if we reject, as we apparently must, the Aptychus 

 of the Carboniferous rocks, referred here by M. D'Orbigny. 



Fig. 08. Capitulum of a Pedunculated Cirripede. a Tergum ; b Scutum ; c Carina ; 

 d Upper latus ; e Carino-latus ; f Rostrum ; g Sub-rostrum ; ft Rostral latus ; Infra- 

 median latus ; k sub-carina. (After Darwin.) 



With the exception of the very ancient Turrilcpas, the oldest 

 pedunculated Cirripedes belong to the genus Pollicipcs, species 

 of which have been discovered in the Rhaetic beds (Upper Trias), 

 and in the Lower Oolites (Stonesfield Slate). In the Cretace- 

 ous period, " the Lepadidae arrived at their culminant point ; 

 there were then three genera, and at least thirty-two species, 

 some occurring in every stage of this system" (Darwin). In 

 the Tertiary rocks are a few species of Scalpdlum and Pollicipes ; 

 but no species of the now existing and widely distributed 



