Cretaceous and Teriidry Cinipeiles. lOJ) 



basal latera, a rostrum, and a subcarina. In liis jjaper 

 (1912) Dr. K. B. Nielsen figured only two of the basal 

 latera f^namely, a rostrum and two rostral latera), but since 

 he still referred the species to PoUicipes, he did not realize 

 the significance of these valves. All the valves of the lower 

 whorl of P. dorsatus are here figured, and their structure 

 agrees in all respects with the species of Sdllcelejids, especially 

 S. carinuta, Scguenza, fnmi the Pliocene of Sicily, and the 

 recent S. superba, Pilsbrv, We are therefore able to prove 

 that a true Scil/ccdepas existed iu the Upper Cretaceous 

 (Dauian), and the importance of this is apparent, since the 

 remaining fossil forms arc S. parona, Alcssandri, from the 

 Pliocene of Italy, and S. carinuta and S. omata, Seguenz;i, 

 from the Pliocene of Sicily. 



Since we can prove that P. dorsatus belongs to Scilleelepas, 

 there is little doubt that P. validus belongs to Scil/ce/epas 

 also, although only the ujjper series of valves and a single 

 rostrum of the lower whorl are known. 



Phyloyenetic Consider at ions. 



In considering the phylogenetic position of the pedun- 

 culate Cirripedes Pycnolepus, Zeutjrnatolepas, Cataatica 

 {Scitlalepas and Titanolepas), and the sessile (Jirripcdc 

 Brachylepas, all represented in the Cretaceous rocks, it is 

 apparent that we are dealing wiih forms that have been 

 evolved from either PoUicipes or a Pollicipes-WVe ancestor, 

 and represent several lines of evolution. All these forms 

 still retain valves of a Pollicipes-Vika character, and, since 

 they are well differentiated in the number, relative position, 

 and structure of the capitular valves, specialization must 

 have begun long before the close of the Jurassic period. A 

 point of s[)ecial interest is the fact that even so early in the 

 Cretaceous as the Cenomanian, two forms, Zevymatolepaa 

 and Titanolepas, had independently developed in the scutum 

 a subccntral uinbo, a tyj)e of valve hitherto known only in 

 the more specialized species of Scalpellum., of which the 

 earliest species occur in the Upper Senonian, A similar 

 development in the scutum is exhibited by the genus 

 Loricu/a, which ranges from Turonian to the Upper 

 Senonian. 



The new genus Pijcnolepas includes a series of spe. ies, 

 ranging from Albiau to Helvetian, in which the capitulum 

 appears to have been formed of eight valves, and the pe- 

 duncle of comparatively large plates. These capitular valves 



