XENOBALANUS GLOBICIPITIS. 443 



The sack extends down to within the almost rudimentary shell : the 

 tunic lining it is unusually strong ; indeed, in the reflexed hood-like 

 portion, it is as strong as the properly external membrane. The latter 

 seems to be moulted in large strips, aud not in a single piece, like the 

 opercular membrane in Balanus : just above the shell, fragments of 

 three or four of these outer coats are retained by their very firm attach- 

 ment to the sheath. The two layers of corium, lining the outer mem- 

 brane of the pseudo-peduncle and the inner tunic of the sack, instead of 

 being, as usual, united almost continuously together, stand some little 

 way apart, and are connected by longitudinal septa ; hence, in a trans- 

 verse section, especially of the lower part, the sack is surrounded by an 

 irregular ring of square tubes of corium. The muscles surrounding the 

 sack and imbedded in the inner fold of corium, are very thinly spread 

 out ; they branch, and even sometimes cross each other ; they are more 

 numerous at the carinal and rostral ends, but certainly cannot be said 

 to form six (or five) bundles, as in all other sessile cirripedes. Some 

 of the fasciae extend down to the very basis, and some up to the sum- 

 mit, to near the two little horn-like projections. I could not perceive 

 any transverse striae on these muscles. Altogether, they are very 

 weak, and cannot have much power in moving the whole peduncle- 

 like body. 



Branchiae. — These are largely developed : they are attached to two 

 approximate, longitudinal, fleshy crests, which extend more than half- 

 way down the sack, along the carinal margin. Each branchia is 

 double, the two folds being united where attached in a transverse line 

 across the sack, on a level with the attachment of the body. The 

 inner fuld is much smaller than the outer ; not extending half so far 

 down the sack, and not extending so far transversely ; it is also hardly 

 at all plicated. The larger and plicated fold extends down considerably 

 below the lower end of the prosoma, and altogether fully equals one third 

 of the entire length of the animal, measured from the shell to the sum- 

 mit of the orifice. Both folds are formed of very delicate membrane. 



Mouth. — Labium unusually prominent, as measured from its basal 

 margin to the crest, which is but slightly notched, hairy, and without 

 teeth. Palpi broad, heart-shaped, clothed on their inner sides by a 

 thick brush of spines, which here, as on the other gnathites and cirri, 

 are almost all doubly serrated. On the outer margin of the palpi there 

 are a few longer spines. Mandibles villose, with five teeth, of which 

 the fifth is very small and of irregular shape : the inferior angle is 

 broad and pectinated. There are no intermediate teeth between the 

 second, third, and fourth teeth, as in the three foregoing genera. Had 

 I not known that the lower main mandibular teeth were always 

 laterally double in the Balaninse, and had I not observed how obscure 

 this structure was in Coronula and Tubicinella, I should have over- 

 looked the merest vestiges of double teeth in the present genus ; in- 

 deed, in some specimens the teeth seemed to be absolutely single. 

 The maxillae are villose : their edge exhibits a trace of being notched 

 under the two great upper spines. The outer maxillae are bilobed, but 

 not very plainly : between these organs there is no little prominent 

 mentum, as in the three previous genera. 



