1G8 Mr. T. H. Witliers on some 



All the fossil species in which the valves are not modified 

 to the extent obtaining in those of Scalpellum were included 

 by Darwin in Pollicipes ; but it is evident no^v that some of 

 these are really primitive forms of Scalpellum {sensu lutu), 

 and that others belong to forms quite distinct from Pollicipes. 

 If we consider that Pollicipes or a Pollicipes-like Cirripede 

 was the ancestral type which gave rise to the various forms 

 of pedunculate Cirripedes and to certain sessile forms, we 

 are not at all surprised to find in the Cretaceous rocks a 

 group of species, which^ while in some instances retaining 

 the Pollicipes type of valve, were modified in respect to the 

 number, relative position, and structure of the valves o£ the 

 cnpitulum. Such forms as the pedunculate Cirrijjedes 

 Zfugmatolepas^, Calantica {Scillcelepas and Tiiano/epas^), 

 and Pycnolepas, gen. nov., and the sessile Cirripede Brachy- 

 lepaSj illustrate this point. 



All of these possess valves which, if found separately, 

 would unhesitatingly be referred to either Pollicipes or 

 Scalpellum (sensu Into), and, indeed, such has always been 

 the case. Zeugmatolepas and Tif.anolepas, however, possess 

 valves which, if found singly, would have been referred 

 some to Pollicipes and others to Scalpellum. 



Hence, until we can piece together the whole or the 

 greater part of the capitulum in certain of the less modified 

 species, it is obvious that no true idea of their affinities can 

 be attained. It is in this direction that future work must 

 lie, and much work is necessary before the phylogeny of the 

 group can be studied with advantage. 



The purpose of this paper is to discuss certain of these 

 forms from this standpoint, with a view to indicating their 

 phylogenetic position. 



Family Brachylepadidae. 



Sessile barnacles in which the shell is composed of an 

 upper whorl of 8 valves, namely, a widely semiconical carina, 

 paired scuta, paired long and narrow upper latera, and a 

 rostrum almost equalling the carina in size, with four whorls 

 of subtriangular imbricating plates encircling the bases of 

 the valves of the upper whorl. Basis probably membranous. 



The family consists of the single genus Brachylepas. 



* Withers, T. H., Proc. Zool. Soc. London, 1913, pp. 938, 943, 



