576 ORDER ABDOMINALIA. 



of the other cirri, but the dorsal spines on their segments 

 are longer. In all ordinary cirripedes the two rami are 

 equally supported by the upper segment of the pedicel, 

 which latter is very short compared with the lower segment, 

 and is separated from it by a transverse articulation. Here 

 (fig. 13) the exterior or anterior ramus is articulated on the 

 pedicel, almost like a branch, in front of the other ramus, 

 which seems more directly continuous with the pedicel. 

 The upper segment of the latter is separated from the lower 

 segment, both being of about the same size, by a very ob- 

 lique articulation. On the front surfaces of the pedicels 

 there are two or three pairs of spines. 



Abdomen. — The three cirri on one side are separated 

 from their opposite pairs by a prominent, longitudinal fold, 

 formed of thickened yellowish membrane, which, when 

 foreshortened by being viewed dorsally, looks like a style 

 projecting immediately beneath the anus. The transverse 

 folds separating the three pairs, are exceedingly slight. The 

 inner basal edges of the pedicels of the cirri project slightly 

 inwards as apodemes, giving, I believe, attachment to some 

 muscles. The anus lies between the posterior pair of cirri, 

 and deeply indents the last thoracic segment. The trans- 

 verse folds separating the three pairs of cirri, little developed 

 as they are, must, according to all analogy, be considered as 

 representing three segments of the body, and as we have 

 accounted for seven cephalic and seven thoracic segments, 

 we must conclude that these are three abdominal segments. 

 We know, moreover, that the abdomen in the pupa? of the 

 Thoracica, with a single exception, does actually consist of 

 three segments. 



Movements of the Mouth, Thorax, and Cirri, 8fc. — Judging 

 from the fact of the lancet-shaped appendage of the labrum 

 being more or less exserted in dead specimens out of the 

 shell-cavity, and from the analogy of other cirripedes, I do 

 not doubt that the whole mouth can be considerably raised 

 and depressed ; we have seen, also, that the rostral end of 

 the toothed orifice of the sack can be pulled down, which 

 would aid in exposing the mouth and labrum. The well- 

 articulated thorax, by the aid of the muscles attached to 

 every segment, can certainly be doubled up and contracted, 



