GENUS CATOPHRAGMUS. 485 



oblique ; the external surface is furrowed by lines of growth. The 

 shell increases a little in diameter, chiefly by the growth of the alse. 

 The parietes are not very thick, with the inner surface smooth, but 

 with punctures placed in rows for the entrance of the tubuli : the 

 laminae of shell alternate with layers of yellow finely punctured mem- 

 brane. Basis formed of thin membrane, in concentric slips. Basal 

 diameter of largest specimen, *6 of an inch. 



Scuta broad, with the lines of growth few in number, but extremely 

 prominent, so as to form folds : basal margin with a very slight angular 

 bend : articular ridge not very prominent. Terga, with a narrow slip 

 along the scutal margin, having the lines or folds of growth so pro- 

 minent as almost to form a series of small transverse pits : the basal 

 margin of this portion forms an angle with the rest of the basal 

 margin : no spur can be said to exist : the crests for the depressor 

 muscle depend a little beneath the basal margin : articular ridge very 

 prominent. 



Mouth : labrum and palpi as in the last species. Mandibles with 

 three main teeth, apparently single, of which the lower tooth has its 

 upper edge pectinated : the inferior part of the mandible is pectinated 

 as usual. The maxillae have two notches, one beneath the two upper 

 large spines, and the other in the middle, separating some thicker and 

 thinner spines. 



Cirri : first and second pairs short, with the anterior rami in each 

 longer by about two segments than the posterior rami ; all the seg- 

 ments thickly covered with bristles. The third cirrus is much longer 

 than the second cirrus, with the posterior ramus longer than the an- 

 terior ramus ; on the latter the three basal segments, and on the pos- 

 terior ramus the two basal segments are thickly covered with bristles ; 

 the other segments have bristles arranged as on the three posterior 

 pairs of cirri, namely, each segment has four pairs of main spines, of 

 which the two lower pairs are short. 



The unarticulated support, whence the articulated portion of the penis 

 arises, is unusually long, equalling the pedicel of the sixth cirrus. 



16. Genus — Catophragmus. PL 20. 



Catophragmus. G. B. Sowerbu.-. Genera of Recent and Fossil 



Shells. Plate. 



Interior compartments eight, icith several exterior whorls 

 of small supplemental compartments : basis either mem- 

 branous or calcareous. 



Distribution, West Indies and Australia. Attached to littoral shells and rocks. 



This genus is very remarkable amongst sessile cirripedes, 

 from the eight normal compartments of the shell being 



