THE SESSILE BARNACLES. 



303 



Cirrus ii has seven and six segments. Among the terminal spines 

 of the shorter (posterior) ramus there is one broader lanceolate 

 spine having two closely toothed edges, but without larger teeth 

 below the serrate portion (fig. 84a). There are three such spines 

 at the distal end of the longer ramus. 



Cirri of the third to sixth pairs much longer than those preceding, 

 and bearing five pairs of spines on the median segments (p. 298, 

 fig. 82/). 



FIG. 84. CHTHAMALUS STELLATUS, NAPLES, a, TERMINAL, SEGMENT OF THE SHORTER 



KAMI'S OF CIRRUS II, SHOWING ONE LANCEOLATE, SERRATE SPINE. 6, PALPOS. C, MAX- 

 ILLA. (1, MANDIBLE. 



The penis is much longer than the last cirri. It is slender, closely 

 ringed, and has a delicate pencil of hairs at the end. 



As this species is the type of the genus, and has been reported 

 from many places all over the world, including our own shores, 

 it has been thought best to give an account of the typical form. 

 Figures 1 to Ib represent topotypes from Naples, which agree fully 

 with Darwin's plate 18, figures la (locality not given) and If 

 (Madeira) ; also with De Alessandri's figures of Italian Pleistocene 

 examples. The opercular valves are highly characteristic. My 

 figure of the entire animal shows only deeply corroded specimens. 



Small specimens up to 3 mm. diameter, but evidently adult, from 

 Fayal, Azores, growing on Purpura hwma-stoma have 10 to 12 very 

 conspicuous ribs. The opercular valves are thin, but typical in form 

 (pi. 71, figs. 4, 



