48 FOSSIL CIRRIPEDIA. 
the tergo-lateral margin more or less protuberant, but not divided by an angle into two 
distinct margins. 
+ Scuta smooth, or marked only with fine lines of growth. 
A. Scuta without any ridge proceeding from the apex to a nearly middle point of the 
basal margin. 
B. Scuta with a ridge, sometimes faint, proceeding from the apex to a nearly middle 
point of the basal margin. 
tt. Scuta either longitudinally or transversely (that is in the direction of the lines of 
growth) ridged. 
As with Scalpellum, the first of the above two paragraphs contains the true generic 
description, as applicable to recent and fossil species ; the second paragraph has been drawn 
up as an aid in classifying separated valves. This, the most ancient genus of the Lepadide, 
seems also to be the stem of the genealogical tree; for Pollicipes leads, with hardly a 
break, by some of its species into Scalpellum villosum ; and Scalpellum leads by Oxynaspis 
into Lepas and the allied genera: Pollicipes mitella, moreover, is nearer allied to the 
Sessile Cirripedes than is any other Pedunculated cirripede, except, perhaps, Lithotrya, which 
is also closely connected with Pollicipes. The six recent species of Pollicipes might be 
divided into three sub-genera: one containing the P. mtel/a ; a second, P. cornucopia, 
elegans and polymerus; and the third, P. spinosus and serta (nov. spec.) Of the fossil species 
some, as P. carinatus, dorsatus, validus, &c., are related to the first section ; others, as 
P. reflexus and concinnus, to the second section ; and lastly, others, as P. glaber and unguis, 
perhaps form a distinct section, though more related to P. mitel/a than to other recent 
species. As, however, most species are known by only a few of their valves, it is scarcely 
possible to speak with certainty regarding their finer affinities. 
Description : as in the case of Scalpellum, the following remarks are confined to the fossil 
species of the genus. In all full-grown recent species the number of valves in the capitulum is 
very large : this seems to have been the case with the Oolitic P. concznnus, and probably with 
most other species, but whether with all may be doubted; from the size of the carinal 
latera of the lower whorl in P. waguis, I suspect that the total number of its valves cannot 
have been great. ‘The valves are either smooth or plainly marked by the lines of growth, 
or they rarely have longitudinal ridges, or transverse ridges corresponding to each 
periodical zone of growth: no recent Pollicipes has a surface of this latter kind. The 
valves in Pollicipes are often strong and massive, with their apices projecting freely from 
the capitulum. 
Scuta generally three-sided, but sometimes, from either the baso-lateral or rostral 
angles being truncated, there is an additional lower side. The tergo-lateral margin is 
either straight or generally more or less convex, but it is never (as far as I know) divided 
into two distinct margins, as is always the case with Scalpellum owing to the abrupt 
ending of the upturned lines of growth. The basal margin is either straight or formed 
