Morjihologyj of some Cretaceous Cirripedes. 'Ml 



ratljcr steeper on tlie carinal side, and a little nearer to the 

 carinal than to the seiital anj^ie. The surlacc of the valve 

 slopes fairly evenly each side of the ridge. The upper and 

 lower earinal margins are straijjht, the upper carinal raar<^iu 

 beinnj about one-third the length of the lower, and forming 

 witli it an angle situated about one-fifth the length of the 

 valve from the apex ; occludent margin slightly convex, a 

 narrow rim along this margin being somewhat protuberant 

 and divided off from the rest of the valve by a parallel 

 depression which is w ider towards the scuta! margin ; scutal 

 margin almost straight, slightly produced Ijelow the pro- 

 tnl)erant occludent rim, and forming with the occludent 

 margin an angle situated nearly two-thirds the distance 

 from the apex. On the inner surface the inner occludent 

 edge is rather narrower than the upper carinal edge, but 

 both edges are narrow and are marked with growth-lines 

 indicating that only a very small part of the valve freely 

 projected. 



Remarks. — This species is characterised not only by its 

 unusually wide and outwardly bowed carina, but by the way 

 in which the inner infilled apical part of that valve is pro- 

 duced into the two lateral and inwardly projecting ridges. 

 Of the specimens from Essen one only (I. 15-Jr49) is not 

 outwardly bent, but this is practically straight and cannot 

 be said to be bowed inwards. It would seem therefore to be 

 a fairly constant character for the carina to be bowed 

 outwards, although in some recent species this feature is 

 often variable. I have not seen a carina of the Gault 

 P.unyuis that is bowed outwards, but of the Chalk P.(jlaher 

 one does rarely come across carinte that are strongly bowed 

 outwards. The scutum of P. bronni is peculiar in the strong 

 inHection of the tergo-lateral portion, and the tergum in the 

 shortness of the upper carinal margin. 



I have not seen any examples of the carina from the 

 Warminster beds referred by Darwin to this species, but, 

 since the outward bending of the carina seems to be such a 

 constant character of P. bronni, I am not at all sure that 

 the Warminster form which is bowed inwards — and what is 

 more important has a more tapering form — can be the same 

 species. 



Phylogenetic Position. 



The capitulum of CretiscalpeJIum is remarkably erect and 

 Sc(il/jellum-Y\kc, and quite unlike the short and rather s(piat 

 niulti-valved capitulum of Pollicipes (Mitclla). In the 

 general build of the capitulum, and the relative position of 



Ann. cfc Maij. N. Hist. Ser. J). Vul. ix. 'Ih 



