~~ 
w 
the Cirripede Genus Stramentum. 
Deseription of Shell. 
Capitulum.—This is-small when compared with, the size 
and breadth of the peduncle, its length being about one- 
fourth that of the shell; evidently the greater part of the 
animal’s body was lodged in the peduncle as in Lithotrya 
and Jéla. 
Scutum subtriangular in outline, with the tergo-lateral 
and basal margins nearly straight and almost at right angles 
to each other; the growth-lines in the lower part of the 
valve follow the outline of the tergo-lateral and basal 
margins. The umbo is situated at a variable distance from 
the apex, and in the more advanced of the Turonian forms 
is about one-third the distance from the apex ; in the Seno- 
nian species, S, haworthi, the umbo is situated at least one- 
half the distance from the apex even in quite young valves, 
and the more advanced forms have the upper half of the 
valve more developed. From the umbo to the apex runs a 
depression from which the upper part of the occludent margin 
rises up. In the figured specimen of S. Haworthi and 
in others on the two slabs there is, on the inner surface, a 
deep pit for the adductor muscle. 
Upper latus almost flat, having the outline of an isosceles 
triangle, with the scutal margin, which abuts against the 
tergo-lateral margin of the scutum for its whole length, 
rather more obliquely inclined and slightly longer than the 
tergal margin. The valve evidently overlapped the tergum 
and scutum very slightly by its edges, and the growth-lines 
are straight and parallel. Darwin said of this valve “The 
first latus now answers to the upper latus in Scalpellum, 
but it is interposed to quite au unprecedented extent between 
the scutum and tergum.”’ It is, however, not more so than 
in the recent Pollicipes mitella, or in the later-discovered 
Cretaceous cirripede Zeugmatolepas mockleri, which perhaps 
is more comparable, since the upper part of the upper latus 
in P. mitella really overlaps the scutum and tergum for the 
greater part of its extent. 
Tergum subtriangular, somewhat convex, with the carino- 
lateral and the upper occludent margins slightly rounded, 
and the basal margin rather more so. The growth-lines are 
convex, and on the upper occludent margin curve sharply 
upwards towards the apex. 
Carinal latus obliquely triangular, rather like the upper 
latus, except that the tergal margin is more obliquely inclined 
and the basal margin more rounded, the valve being slightly 
inclined towards the tergum. 
