the Cirripede Genus Stramentum., 77 
sively prove that the shell of Stramentum was composed of 
ten vertical series of plates, five on each side of the shell. 
Since there were no keeled plates to the capitulum, and 
the subcarinal and subsecutal plates of the peduncle did 
not intersect or overlap each other, the shell could be 
readily divided along the median line thus formed without 
destroying any one plate. This is exemplified by the fact that 
ou the two slabs of chalk from Kansas on which about thirty 
. individuals are preserved, no less than twenty-eight of them 
consist of one side of the shell more or less complete, and 
show the inner surface. The other side of these shells was 
probably on the counterpart of the slab, or had floated away 
after the death of the animal and decomposition of the soft 
parts. Iu individual cases one side of the shell might easily 
_ be torn away by some animal, as suggested by Darwin. 
Growth.—New scales of the peduncle are apparently first 
formed round its summit towards its carinal end, for, as 
pointed out by Darwin, there is in the holotype of S. pul- 
chellum one more scale under the second latus and oue more 
under the first latus than under the scutum. In the figured 
specimen referred to S. darwint by Dr. Woodward, there 
appears to be two more scales in both the series than in that 
under the scutum. One very young example of S. haworthi 
is here figured (Pl. LV. fig. 1 A), measuring 4°2 mm. in length 
and. consisting of twelve plates only to its nearly complete 
peduncle. 
Attachment.—Darwin was of the opinion that in this genus 
the attachment was probably by one lateral face of the lower 
part of the peduncle, and was effected either by the overflow 
of the cementing material from the two central original 
orifices or by cement poured out of orifices situated on one 
side of the peduncle. He found no difficulty in the peduncle 
ending in so fine a point, for he stated that in Scalpellum 
vulgare the peduncle, when carefully dissected from the 
coralline to which it is attached, is often found to end in a 
much finer pot and to be symmetrically attached to the 
branch by its narrow rostral margin. 
Dr. H. Woodward (1908, pp. 498 e¢ seq.), however, con- 
sidered that the peduncle was attached along the whole 
extent of the subscutal and subcarinal scales, and that the 
mode of growth of Stramentum was always prone. He 
concluded, since Darwin mentioned that S. pulchellum was 
found “embedded outside the cast of an ammonite,” that 
‘he did not quite realize it was adhering to the shell and 
parasitic upon the ammonite, as Coronula balanaris attaches 
itself to the skin of the whale, and Chelonibia tesludinariu and 
