454 BALANIDJ2. 



dorsal surfaces of these segments, in some of the species, 

 are serrated in an upward direction. 



Bod//, 8fc. — The body does not present any particular 

 character : in C. scabrosus there is a slight ridge running 

 from the base of the first cirrus towards the adductor 

 scutorum muscle : this ridge is clothed with a few hairs ; 

 there are also some hairs at the carinal end of the sack. In 

 C. dentatus, also, there are hairs on the outer tunic of the 

 prosoma. In two species which I opened, there were no 

 ca3ca to the stomach. The ova vary in length from 

 1 |Jy 4 th of an inch in length; they are packed in two lamella? 

 lying on each side of the animal's body. The larva just 

 escaped out of the egg, in C. stellatus, scabrosus and dcn- 

 tatus, had a large probosciformed mouth. 



Branchice. — These present a very singular amount of 

 difference within the limits of the same genus. In 

 C. stellatus and antennatus we have a simple fillet, tapering 

 a little, barely plicated, and about half, or more than half, 

 as long as the sack ; in C. scabrosus the branchiae are entirely 

 aborted, or are perhaps represented by the slight hairy ridge 

 at the carinal end of the sack : in C. dentatus, on the other 

 hand, each branchia consists of two large folds, barely 

 plicated, almost covering the whole side of the sack, so that 

 here the branchiae are developed to an unusual degree, 

 more than in Balanus, and as in Coronula and its allies : in 

 the same manner as in these latter genera, the outer fold is 

 considerably larger than the inner fold. 



Affinities. — C. intertextus is the most distinct species 

 of the genus, as shown by the peculiar radii and ala:, by 

 the scuta and terga being calcified together, by the character 

 of the third pair of cirri, and by the inflected parietes 

 forming a ledge round the membranous basis ; but in this 

 latter respect C. intertextus resembles C. Hembeli. C. Hembeli, 

 in its serrated radii, is closely related to C. dentatus ; and 

 this latter species differs in the structure of its radii only 

 in degree from certain varieties of C. stellatus. Lastly, 

 C. intertextus, in its peculiar radii, closely resembles C. 

 scabrosus, and this latter species does not differ much from 

 the other species. Hence the genus Chthamalus has no 

 claims to be subdivided into smaller genera. 



