(sect, e), balanus declivis. 275 



trebling the irregular rows of short tubes in the walls of B. halanoides, 

 with their reticulated inner lamina and longitudinally folded outer 

 lamina, we should have the structure exhibited in B. cariosus. We 

 have seen, also, that in var. (a) of B. halanoides, the spur of the 

 tergum is remarkably sharp, as in B. cariosus. This species, also, in a 

 very marked manner approaches in many characters, especially in the 

 opercular valves, in the cirri, and to a certain extent in the shell and 

 basis, to B. flosculus, and even in external appearance to var. sordidus 

 of the latter — an inhabitant of the opposite extremity of the continent, 

 namely, of Tierra del Fuego. Again, the tergum to a certain extent, 

 and the scutum in a singular manner, resemble these valves in B. 

 nubilus, showing an unequivocal affinity to that species. With respect 

 to the most remarkable character of the species, namely, the several 

 irregular rows of tubes or pores in the walls, it deserves notice that in 

 B. crenatus, which is certainly closely allied to B. halanoides, the 

 longitudinal septa sometimes divide near the outer lamina, thus giving 

 rise to a few additional tubes. Of the above several species, to which 

 our present species is allied, B . flosculus stands in the next section, and 

 B. nubilus and crenatus in the last : hence we see that B. cariosus 

 has singularly divergent affinities. The peculiar structure of the 

 parietes, together with the general appearance of the shell, made me at 

 the first moment suppose I was examining a Tetraclita (or Conia 

 of Leach) ; hence, also, it has arisen, that Lepas cariosa of Pallas 

 has often been quite erroneously given as a synonym of Tetraclita 

 porosa. 



31. Balanus declivis. PL 7, fig. 4# — 4<d. 



Parietes solid ; rostrum nearly twice as long as the carina 

 or carino-tateral compartments, hence the basis is oblique. 

 Tergum with the spur truncated, half as wide as the valve. 



Hah. — West Indies ; Mus. Brit. — Jamaica, imbedded in a sponge ; Mus. 

 Cummg. 



This is a remarkable species ; when first seeing it 

 imbedded in numbers in a sponge, I did not in the least 

 donbt but that it was an Acasta : on examination, however, 

 it is found to have a membranous basis, and therefore 

 cannot by the definition enter into that sub-genus, to 

 which, however, it is very closely allied. It differs from 

 other sessile cirripedes very remarkably in the rostrum 

 being nearly twice as long as the carinal compartments, so 

 that the basis is always very oblique, or placed almost on 

 one side ; in this elongation of the rostrum, although in a 



