52 FOSSIL CIRRIPEDIA. 
of growth. The remarkable straightness of the tergo-lateral margin of the scuta is like that 
in the recent P. spinosus and serta, and in Scalpellum villosum, in all which species, 1 may 
observe, the scuta and terga are separated by an interspace of membrane; in these three 
recent species, however, the basal margin is considerably protuberant. ‘The present species 
differs apparently from the P. concinnus of the Oxford clay, in the basal and tergo-lateral 
margins of its scuta being straight; in the greater proportional length of the scutal and’ 
1 3. Po.uicrpes Niussoni. Tab. III, fig. 11. 
Potuicires Nitssoni. Steenstrup. Kroyer, Naturhist. Tidsskrift, 1839, pl. v, figs. 20—23. 
P. scutis triangulis, planis: margine basali cum margine occludente angulum pene rectum, cum margene 
recto tergo-laterali, angulum aliquanto minorem formante. Deest segmentum tergo-laterale, lineis incrementi 
reflexis formatum. Carind introrsis admodim arcuatd, crassd ; marginis basalis mucrone obtuso. 
Scuta triangular, flat; basal margin forming nearly a rectangle with the occludent margin, and a 
somewhat lesser angle with the straight tergo-lateral margin. There is no tergo-lateral slip formed by 
upturned lines of growth. Carina much bowed inwards, massive, with the basal margin bluntly pointed. 
Scania (Balsberg, Kopinge, Ffo., &c.) Mus. Univers. Copenhagen. 
Professor Steenstrup has described, under the name of Pollicipes Nilssonii, a large carina, and appa- 
rently a sub-carina and rostrum, and he remarks that these perhaps belong to the same species with the 
terga, named by him P. undulatus. M. Angelin, however, believes that the latter belong to the species 
already described as Scalpellum solidulum, With the specimens of the present species, M. Angelin has 
lately found three small scuta, which he believes belonged to it. These scuta are so extremely worn, 
that I should not have ventured to have named them, had it not been advisable to give figures of the 
remarkable carina already named as P. Nilssonii. Should it hereafter be proved that the following scuta 
belong to some other carina, then a new name will have to be attached to them. 
Scuta (fig. 11, a) flat, thick, triangular, not much acuminated ; basal margin forming almost a rectangle 
with the occludent margin; tergo-lateral margin (in present condition) straight, forming a rather less 
angle with the basal than does the occludent margin. There is no trace of a slip or portion of valve along 
the tergo-lateral side, formed by upturned lines of growth. Internally, the pit for the adductor muscle is 
deep ; the central portion of the apex above the pit is prominent; apparently there was no internal furrow. 
Length of longest specimen only ‘4 of an inch. 
Carina (fig. 11, 6, c) strong, with the upper part unusually massive; though in a worn condition, 
there are distinct traces of its having been longitudinally and slightly ribbed. Strongly carinated, the two 
arched sides meeting each other at about a rectangle; much bowed inwards, and widening much from 
the apex to the base; upper portion, about one fifth of the entire length of the carina, seems (for the 
worn condition prevents certainty) to have projected freely; beneath the upper freely projecting portion, 
the inner margins are nearly straight ; the depth of the shell, measured from the central crest to the inner 
margin, is, in the lower half, remarkably great, and consequently the valve in the same part is internally 
concave to a remarkable depth; the upper freely projecting portion is only slightly concave, and is singu- 
larly massive, from having been filled up with solid shelly layers. The basal margin is bluntly pointed, 
the edges meeting each other at about a right angle; in the lower part of the valve the lines of growth 
are of course parallel to the basal edges, but higher up they meet at a more open angle, and consequently 
the carina of a young individual must have had its basal margin less projecting. When the sides of the 
carina are examined carefully, a portion, about one fourth of its entire depth, can be observed to lie a very 
little more inwardly inflected than the more central part, so as not to form quite a continuous surface with 
