Morphology of some Cretaceous Cirripedes. 373 
(Pl. V. fig. 1) to be the inframedian latus, and it follows 
from this that the other valve must be the rostral latus. 
Two similar valves were exhibited apart from each other 
on specimen J. 1573 (PI. V. figs. 44,6), and these may 
have belonged to a single individual. In both specimens 
44300 and I. 1573 the two valves, although much larger, 
are exactly similar in structure to the two attached valves 
(Pl. V. fig. 5) figured by Darwin (1851, pl. iv. fig. 1 4), 
and consequently the latter valves are the /efé rostral and 
inframedian latus, and not right-hand valves as supposed by 
Darwin. Moreover, in all the specimens, these two valves 
il. 
Scalpellum (Cretiscalpellum) unguis (J. de C. Sowerby). Albian, Gault: 
Folkestone, Kent. Restoration of capitulum. 
c, carina; s, scutum; ¢, tergum; w./., upper latus; ¢./., carinal latus ; 
1.1, inframedian latus; 7./., rostral latus ; 7, rostrum; s.c., subearina. 
show that the rostral latus was not only overlapped by the 
inframedian latus, but the two valves are very similar in 
shape and size. Consequently, if the rostral latus was 
placed in position beneath the inframedian latus in the 
specimen 59802 (Pl. V. fig. 1), there would be no room 
for further latera. 
So far, then, we have proved that the capitulum consisted 
of a carina, two scuta, two terga, two upper latera, and three 
pairs of lower latera only, making thirteen valves in all. In 
addition, we know that there was a large rostrum, and 
Darwin figured a valve which he called a subrostrum. I can- 
not conceive how the latter valve could have formed part of 
