306 BALANID.E. 



those in Balanus. The outer maxillae and palpi appear 

 unusually prominent : the labrum is deeply notched, with 

 no teeth, or very obscure teeth on each side. The mandibles 

 have five teeth, but the fifth is sometimes confluent with the 

 inferior angle. The maxillae are not notched ; and carry one 

 or two spines, near their inferior angle, nearly as large as the 

 upper pair. The outer maxillae are bilobed. 



Cirri: in the first pair, the rami are very unequal in 

 length, the one ramus being from half to one-third of the 

 length of the other. The segments in the second and third 

 pairs, are not so much broader, or so much more crowded with 

 bristles, in comparison with the three posterior pairs, as is 

 the case with most species of Balanus. The three posterior 

 pairs, except in A. purpurata, are much elongated, and the 

 long thin segments bear four, and sometimes only three, 

 pairs of spines, which are generally doubly and finely 

 serrated, or even feathered. The most remarkable fact 

 respecting the cirri, is, that in A. spongites, sulcata, cgathus, 

 and glans, the fourth pair, instead of being identical in 

 structure, as in all other genera, with the fifth and sixth pairs, 

 has, on its anterior ramus, the pairs of spines more crowded 

 together, with the little intermediate spines, and those in 

 the dorsal tufts, a little longer than in the sixth cirrus ; and 

 between the pairs of spines, there occur some straight, up- 

 wardly pointed, very minute, and very thick spines or teeth. 

 And, what is still more remarkable (as will hereafter be 

 described in detail), in certain specimens, but not in all, of 

 A. sulcata, the front surfaces of the lower segments on the 

 anterior ramus, are developed into thick, small, downwardly 

 curved, hook- like teeth ; this likewise is the case with the 

 upper segment of the pedicel (PL 29, fig. 2), — a most 

 elegant, mandible-like organ for the prehension of prey being 

 thus formed. The variability of such beautifully contrived 

 teeth is very surprising. Some similar teeth occur on the 

 segments of the anterior ramus of the fourth cirrus, but not 

 on the pedicel, in A. cgathus. A few teeth resembling the 

 above, but thicker, occur on the segments of the anterior 

 ramus of the same cirrus, in A. purpurata. 



Branchice, 8fc. — In A. spongites, I found the branchiae 

 rather small, with transverse plications. The muscles of the 



