Cretaceous and Terti'ari/ Cirripedes. 191 



paratively large and less likely to be overlooked. It is true 

 tliat the u[)per lutus ot P. paronai has not yet been found, 

 but this probably being long and narrow would be more 

 liable to fracture. ^lost of the valves of this speeies are 

 much fractured. 



The eai)itular valves of Pi/cnolepas agree with those of 

 Bravhylepas in number and disposition, but differ in the far 

 less width of the carina and rostrum. The main difference 

 from Brachijlepas lies in the plates of the peduncle, for these 

 are all of one type, and could not have formed a series of 

 whorls as in Brachijlepas. in any case there is a gi'cat 

 structural difference from Brachijlepas, and since the species 

 differ from those of the typical Pollicipes in the small 

 number of valves to the capitulum, they are placed in a new 

 genus Pycnolepas. 



With respect to the scuta, P. riyidus is distinguished by 

 the narrow, wall-sided, apico-basal ridge and in the pro- 

 duction of the basi-lateral portion of the valve. P.fallax is 

 readily distinguished l)y the apico-basal ridge having a sharp 

 edge with sloping sides, as well as by the absence of longi- 

 tudinal ridges. P. paronai and P. brilnnichi both have a 

 very broad apico-basal ridge, but while in P. brilnnichi it is 

 much raised, flat-topped, and with perpendicular sides, in 

 P. paronai it is flatly rounded. The ^cnixxvn oi P . paronai 

 is further distiuguislied by the wavy longitudinal ridges 

 radiating from the apico-basal ridge, and that of P briinnichi 

 in being less elongate than that of the other species. 



In the terga P. /aZ/a.z' is at once distinguished by the apico- 

 basal ridge having sloping sides : this ridge in P. riqidus is 

 narrow and has perpendicular sides ; in P. paronai it is only 

 slightly broader than in P. riyidus, but the valve can be 

 distinguished by the straightness of the ridge. P. paronai 

 dilTers from P. brilnnichi in the presence of wavy longi- 

 tudinal ridges radiating from the apico-basal ridge. 



Seguenza (1876, Atti Accad. Pontaniana, vol. x. p. 395) 

 doubtfully referred Pollicipes riyidus and P. eleyans ( = P. 

 brilnnichi), together with P. gracilis, P. validus, and P. dor- 

 satus, to his genus Scillcelepas. Alessandri, however (1906, 

 Paheont. Ital. vol. xii. pp. 249, 264), judging mainly by the 

 form of the scuta, considered that P. eleyans and P. riyidus 

 could not be referred to Scillcelepas, but that they agreed 

 much more closely in the form of the scuta with Pollicipes. 

 He therefore referred the species P. riyidus and P. elegans, 

 together with P. fallax and P. paronai, which, have a precisely 

 similar form of scutum, to the genus Pollicipes. In Scillee- 

 lepus the upper whorl consists of 5 \alves, namely, carina. 



