The flexor and extensor muscles, which, as I believe, move the upper segment of the pedicel (_a_ and _b_, Pl. 29, fig. 1), are attached at their upper ends to its basal margin, and are thus enabled to draw it a little way down within the lower segment, and so move it. The short flexor muscle (_c_), which is attached at its lower end within the upper segment of the pedicel, and the longer extensor (_d_), also, attached within this same lower segment, serve, I believe, to move the lower, partially confluent segments of each ramus as a whole. In the case of these muscles, and of those last mentioned, I am surprised that the extensors (_b_) and (_d_) are not attached nearer to the exterior and dorsal surface. Other muscles (_e_, _f_) attached at their lower ends within the upper segment of the pedicel, run up each of the two rami to their tips, with some of the fasciæ terminating within each segment: of these muscles, the outer one (_f_, _f_) appears to be the extensor, and the inner one (_e_, _e_) the flexor. But besides these, there are other short flexor muscles (_g_, _g_) which run on the anterior face,[31] from segment to segment, serving to pull the front edge of one segment within the edge of the next lower segment. These muscles differ much in plainness in the several genera: they are very distinct in Coronula. In some specimens of this genus, a few of the articulations between the basal segments of the rami having been obliterated, the short muscles (_g_, _g_) running from articulation to articulation were absent, and their presence and nature in the upper segments thus rendered the plainer. The muscular system in the several pairs of cirri seems to be the same, with the exception of the first pair, in which the muscle answering, as I suppose, to (_a_), namely, the flexor of the upper segment of the pedicel, is much spread out at its lower end, and is there attached to the exterior surface of the lower segment. [31] For a considerable time I thought that there were muscles going to the spines, especially to those which arise from the upper dorsal edge of each segment; but I have since ascertained that these are the cases within which new spines, with their lower ends doubled like the fingers of a glove hastily pulled off, are in process of formation.