22 T. M. Withers — Cirripedes from the Chalk. 



S. tuberadatum, Darwin, constitutes a further advance, for in this 

 form the umbo of the scutum is in a sub-central position, the umbo of 

 the carina being still apical. In the more advanced forms the carina 

 as well as the scutum has the umbo in a central or sub-central 

 position, and the growth of the valves proceeds in two opposite 

 directions. As yet, only one Cretaceous species in which either the 

 carina or scutum has this advanced type of growth has been recorded 

 with certainty from England, namely S. tuberculatum. This species 

 was collected by the late William Harris from the Chalk detritus of 

 Charing, Kent, but unfortunately its exact age is doubtful. 



The occurrence of S. Barioinianum, Bosquet, is therefore of great 

 interest as being the first record of an English species in which the 

 umbo of the carina is sub-central, and the growth consequently in two 

 directions. The species has been found by Dr. Blackmore in the 

 zones of Actinocamax quadratics and of Belemnitella mucronata. 



Including those described in this paper, there have been nearly forty 

 species of Scalpellum described from British and foreign Cretaceous 

 rocks. Of these, only five have either the carina or scutum, or 

 both, with the growth proceeding in two opposite directions ; namely, 

 Scalpellum tuberculatum, Darwin, S. Darwinianum, Bosquet, from the 

 Chalk of this country ; and >S. Beisseli, Bosquet & Muller, 8. Bar- 

 xoinianum, Bosquet, S. Hagenovium, Bosquet, and S. radiatum, 

 Bosquet, from the Upper Senonian and Maestrichtian of Holland and 

 Belgium, and other foreign localities. 



The significance of this will be seen when it is noted that a much 

 larger proportion of the Tertiary species have this double direction of 

 growth, and among the recent species the percentage is still higher. 



Loricula expansa, sp. nov., is also of much interest, since it represents 

 a further development in the scutum, the umbo of which is situated 

 in a much more central position than in the other forms of Loricula. 

 Unfortunately the scutum is the only valve known, but owing to its 

 great importance it is thought advisable to describe it, especially as 

 it is represented by five examples. 



It is therefore apparent that there is a close connexion between 

 the geological age of the forms and the position of the umbo in certain 

 valves of the capitulum, and this feature is consequently of great 

 phylogenetic importance. 



To facilitate the interpretation of the isolated valves here described, 

 figures are given in the text in which the valves of the capitulum are 

 in position. (See Figs. 1, 2, p. 21, and Eig. 7, p. 28.) 



Scalpellum Darwinianum, Bosquet. Eigs. 3, 4. 



1854. Scalpellum Darwinianum, J. Bosquet, Les Crust. Foss. du Terrain Cretace 



du Duche de Limbourg, p. 46, pi. iii, figs. 6-12. 

 1854. S. Darwinianum, C. It. Darwin, Kay Soc. Monogr. Sub-class Cirripedia, 



Synopsis et Index Systematicus, p. 631. 

 18S0. S. Darwinianum, Th. Marsson, Mittheil. natunv. Vereine von Neu- 



Vorpomraern und Riigen, Jahrg. xii, p. 4, pi. i, fig. 1. 

 1888. S. Darwinianum, A. Peron, Bull. Soc. Sci. Yonne, vol. xli, p. 270, pi. iii, 



figs. 1-4, 1887. 



This most interesting species, hitherto unrecorded from the English 

 Chalk, is represented in Dr. Blackmore' s collection by five carinas and 



