GENUS CHTHAMALUS. 447 



Looking to the animal's body. The Labrum is always 

 swollen and bullate,and though hollowed out, is never notched 

 in the middle. The Palpi are rather small, and have not their 

 tips nearly touching each other. The mandibles generally 

 have their lower main teeth laterally single, though some- 

 times they are double : the inferior angle is always pectinated. 

 The maxillae are always notched under the upper pair of 

 great spines. Of the Cirri, the third pair much more closely 

 resembles, in external structure and powers of movement, 

 the fourth than the second pair, though sometimes a few 

 of the basal segments, especially on the anterior ramus, are 

 thickly covered with bristles, as on the segments of the 

 second pair. In three species belonging to two genera, 

 there are caudal appendages, resembling those generally 

 present amongst the Lepadidae, but never found in the 

 Balaninae. The Branchiae are generally smaller than in the 

 Balaninae ; and are sometimes quite rudimentary. 



In the introductory description (p. 152 and 176) of the 

 Family Balanidae, I have already discussed the relations of 

 the Chthamalinae to the Balaninae, and of the several genera 

 to each other, so that I need not here re-enter on the sub- 

 ject. 



12. Genus — Chthamalus. PI. 18, 19. 



Chthamalus. Ranzani. Memoire di Storia Naturale, 1820. 

 Euhaphia. Conrad. Journal Acad. Nat. Sc. Philadelphia, vol. 7, 

 1834. 



Compartments six: basis membranous, but sometimes in 

 appearance calcareous, oioing to the i?rflected parietes. 



Distribution mundane ; attached generally to littoral rocks and shells. 



This, the typical genus, is the largest and widest distri- 

 buted group of the sub-family Chthamalinse. The founder 

 of the genus apparently did not perceive its essential 

 character ; Savigny, however, as is evident from the excellent 

 figure in the great work on iEgypt, perfectly understood 



