the Cirrjpede Subgenus Scillaslepas. 261 



margin very sliglitly convex, almost, sfraiglit, not divided 

 into an upper and a lower portion ; occludent margin gently 

 convex, almost straight, and forming with the carinal margin 

 an angle ot" about 35° ; scutal margin slightly convex, rather 

 longer than the occludent margin, with which it makes a 

 rounded angle. The valve is ornamented similarly to the 

 carina, but the longitudinal lines are more apparent. 



Subcarifia more than half as wide as long, not nearly so 

 strongly convex as the apical portion of either of the two 

 carina ; basal margin slightly convex. The inner surface of 

 the valve slopes towards tlie outer surface and forms a sharp 

 edge, so that there is no possibility of thi^ valve being merely 

 the broken off apical portion of a carina. 



Systematic Position o/Calantica (Scillpelepas) gaveyi. 



Darwin, in his Monograph (1851), referred the known 

 Jurassic species (Pollicipes concinnus, Morris *, P. oolificus, 

 Buckman f, and P. jJ^anulatus, Morris X) to the genus Polli- 

 cipes. Now the distinguishing characters of Pollicipea, whicli 

 is essentially a recent genus, and evidently a polyphyletic 

 one, is the downward growth of the valves, and their large 

 number (from eighteen to over one hundred). Certainly the 

 valves of the above three species have a downward growth, 

 and since there is evidence in only one species — P. concinnns 

 — that the valves numbered more than eighteen, Darwin must 

 have relied on the downward growth of the valves, and 

 almost as certainly on the distinctive characters of the detached 

 valves as compared with those in the genus Scalpellum. 

 Scalpellum has more modified valves, numbering from twelve 

 to fifteen. 



Two further genera have since been established whicii 

 embrace Jurassic species — nan\ely, Archceolepas, Zittel § 

 (1884), and Pycnolepas, Withers |1 (1914), the former in- 

 cluding the species PolUcipes redtenhacheri, Oppel, Poliicipes 

 royeriy de Loiiol, and PolUcipes quenstedti, von Ammon, and 

 the latter including certain Cretaceous species, together with 



* Morris, J., 1845, Ann. & Mag. Nat. Hist. ser. 1, vol. xv. p. 30, pi. vi. 

 fig. 1 ; Darwin, C. II., 1851, Pal. Soc. Monogr. Lepadidic, p. 50, pi. iii, 

 tig. 1. 



t Buckman, J., 1844, Qeol. Cheltenham, p. 95, pi. iii. fig. 7 ; Darwin, 

 C. R., 1«51, Pal. Soc. Mf)nogr. Lepadidae, p. 50, pi. iii. fig. 2. 



X Morri.s, J., 1845, op. cit. p. 31, pi. vi. fig. 2. 



§ Zittol, K. A. von, 1884, Sitzungsb. k. b. Akad. Wiss. Miinchen, 

 Bd. xiv. Heft iv. p. .''.81. 



II Withers, T. II., 1914, .\nn. ^: Mitg. Nat. Hist. .<?er. 8, vol. xiv. 

 pp. 170, 200. 



