T. H. Withers—Pollicipes levis, Sby. 499 
p- 64, pl. iv, fig. 1) figured a number of valves belonging to a single 
individual, namely, a carina, a pair of terga, a rostrum, a sub-rostrum, 
a pair of upper latera, a pair of latera of the lower whorl from the 
carinal end of the capitulum, and two other latera of this same whorl 
from one side of the rostral end of the capitulum. These are preserved 
in the Museum of Practical Geology, Jermyn Street. Darwin says of 
the scutum: ‘‘ Although the scutum is, unfortunately, at present 
unknown, there can be scarcely any doubt that it would closely 
resemble that of P. glaber, and therefore I have not hesitated, in 
this instance, to break through my rule of exclusively taking the 
scutum as typical in Pollicipes: should, hereafter, a scutum be found 
in the Gault like that of P. glaber, it may, with considerable confidence, 
be named as belonging to this species.’’ 
Fic. 
4. Pollicipes unguis, J. de C. Sowerby. External view of the right side of part of 
a capitulum of a young individual. x 6diam. Albian, Gault: Folkestone, 
Kent. B.M., 1.13523. c. carina; s. scutum; ¢. tergum; /. upper latus ; 
¢./. carinal latus. 
5a. Id. External view of right scutum of a much older individual. x 2 diam. 
5b. Id. ue surface of same, showing the deep pit for the adductor scutorum 
muscle. 
In the British Museum (Natural History), registered I. 13523, 
there is a young example of P. wnguis, with several of the valves of 
the capitulum in position (Fig. 4). Theright side of the capitulum is 
uppermost, and shows the carina, scutum, tergum, upper latus, and 
cearinal latus. Its importance lies in the fact that the valves are almost 
in their original positions, and that it includes the scutum, which 
has not been described previously. The portion of the capitulum 
preserved is twice as long as wide. Its greatest length is 9mm. and 
its greatest breadth 4.5mm. With the exception of the scutum the 
various valves of P. wnguis have been fully described by Darwin, 
and in these circumstances it is proposed here to describe the 
scutum alone. 
The description of the external characters of the scutum is based 
