528 MR, T. H. WITHERS ON 



27. Some early Fossil CirripeJes of the Genus Scalpellum. 

 By Thomas H. Withers, F.G.S.* 



[Received January 31, 1912 : Read March 19, 1912.] 



(Text-figs. 64 & 65.) 



Index, 



Page 



Structnre of curiua oi Scalpelht77t 528 



Evolution of early fossil forms of Sea?peZZ«»j 630 



Distribution (Geological) of Cretaceous Scalpelhim 537 



Sea Ipellum arcuatum Darwin 532 



S. trilineatum Darwin 531 



ScaJjpellum s-p-p. — discussion of affinities 538 



Among the Cirripede remains from the Albian (Ganlt) of Folke- 

 stone in the collection of the British Museum (Natural History), 

 three detached valves were noticed, which, for certain reasons to 

 be explained later (see p. 532), appear to he the original valves 

 upon which Darwin founded the species Scalpellum arcuaticm f. 

 A portion of one of the valves, a carina +, happened to be broken 

 away from its matrix, showing that the inti'aparietes, said by 

 Darwin to be absent in this species, were really present. These 

 parts, however, are developed in such a way that they can be 

 seen only by cleaning the valve free from matrix. The finding 

 of the intraparietes in Darwin's type of /S. arcuaium led to the 

 examination of further examples of the carina, and the fact was 

 established that intraparietes are developed in all carinas of this 

 species, 



S. trilineatum Darwin (1851, p. 38, pi, i, fig. 5), from the 

 Cenomanian (Grey Chalk) of Dover, was said by Darwin to come 

 nearest to S. arcuatum, owing to the absence of intraparietes. 

 The carina, which is the holotype of *S', trilineatum, is in the 

 British Museum (Natural History), registered 38461, On freeing 

 this specimen from the gum and matrix which obscured the inner 

 portion of the valve, it was at once apparent that not only were 

 the intraparietes present, but that they were developed almost 

 exactly as in S. arcuatuin. 



Other Lower Cretaceous species of Scalpellum in which the 

 intraparietes of the carina are said to be absent are S. simplex 

 Darwin (1851, p, 39, pi, i. fig. 9) and S, accumidattcm Withers §, 

 both of which come from the Aptian (Lower Greensand), The 

 xniique carina of ^S*. simplex cannot at present be traced, but since 

 the parietes do not reach to the basal margin of the valve (see 

 text-fig. 64, 1) as in those carinas which have intraparietes, it 

 does not appear probable that intraparietes could be present. In 



* Communicated by Dr. W. T. Calman, P.Z.S. 



t C. R. Darwin, 1851, Pal. Soc. Monogr. Foss. Lepadidse, p. 40, pi. i. fig. 7. 



J For the names of the various valves see text-fig. 65. 



§ T. H. Withers, 1910, Gcol. Mag. dec. v. vol. vii. p. 152, figs. 1-1. 



