the Cirripecle Genus Stramentnm. 77 



sively prove that the shell of Stramenlum was composed of 

 ten vertical series of plates, five on each side of the shell. 

 Since there were uo keeled plates to the capituluni, and 

 the subcarinal aud subscutal plates of the peduncle did 

 not intersect or overlap each other, the shell could be 

 readily divided along the median line thus formed Avithout 

 destroying any one plate. This is exemplified by the fact that 

 on 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, aud 

 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. In individual cases one side of the shell might easily 

 be torn away by some animal, as suggested by Darwin. 



Groivth. — 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- 

 chtUum one more scale under the second latus aud one more 

 under the first latus than under the scutum. In the figured 

 specimen referred to S. darivini 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. haivortJii 

 is here figured (PL IV. fig. 1 A), measuring 1"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 Scidpellum 

 vulgare the peduncle, when carefully dissected from the 

 coralline to which it is attached, is often found to end in a 

 much finer point and to be symmetrically attached to the 

 branch by its narrow rostral margin. 



Dr. II. Woodward (1908, pp. 498 et 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 Stramentuvi was always prone. He 

 concluded, since Darwin mentioned that S. pulchellum was 

 found "embedded outside the cast of an ammonite,'^ that 

 " lie did not quiie realize it was adhering to the shell aud 

 parasitic upon the ammonite, as Coronula balanaris attaches 

 itself to the skin of the uhalo, and Chelunibia Itsiudinuriii and 



