THE SESSILE BARNACLES. 



313 



spur, wliich is wholly united with the basiscutal angle. The carinnl 

 lobe is narrow, situated high, and shows a feAv short crests for the 

 depressor muscle. 



The labrum has a broad, nearly straight edge, the middle fourth 

 having a series of 18 strong teeth (fig. did). The mandible has 

 three large teeth and a pectinated lower point having eight slender 

 teeth (fig. 91a). 



The maxilla has a pair of large upper spines followed by two 

 smaller spines above the small notch. The median part bears a group 

 of about 8 rather large spines. The lower third protrudes, and 

 bears about 10 large and small spines. There is a group of short 

 spines on the lower edge. The prominence of the lower part is a chief 

 feature (fig. Olr). 



•rtMAAMAAWWWi,^,,.^ 



Fig. 91. — Chtiiaxiali-.s withehsi. a, mandible, b, eleventh segment op cirrcs vi. 



Cj maxilla. (1, DPPEK MAIKilN OF THE LABRU.M. 



The first cirrus has rami of 9 and 5 segments, the posterior branch 

 two-thirds as long as the anterior. 



Cirrus ii has 9 and 8 segments, the rami proportioned as in cirrus i. 

 Xone of the spines in the distal segments are pectinated or plumose. 



Cirrus iii has rami of 19 segments, bearing three pairs of spines. 



Cirrus vi has rami of 23 segments, also with three pairs of spines 

 (fig. 915). 



The chief characteristic of this species is the weak articulation of 

 the scutum and tergum ; the articular ridge of the scutum is short 

 and extremely weak, and the articular furrow is shallow. The shape 

 of the tergum is peculiar. These features will at once separate 

 C withersi from the smooth, unworn forms of C. stellatus. The ab- 

 sence of pits for the adductor and depressor muscles is also notable. 

 In the mouth-parts, the labrum and mandible diil'er widely from 



