224 BALANID.E. 



the valve, with the end truncated, situated either near or quite close to 

 the basi-scutal angle. The crests for the depressor muscles are mode- 

 rately well developed. 



Compartments. — The parietal tubes are, in their upper parts, filled 

 up solidly, without transverse septa. The radii generally have their 

 summits slightly oblique, and this is almost always the case with 

 the radii of the rostrum ; the other radii sometimes extend from tip to 

 tip of the parietes, and are parallel to the basis ; rarely the radii are con- 

 siderably oblique. The septa of the radii are very obscurely denti- 

 culated, and the interspaces between them are filled up solidly. The 

 alse have their sutural edges thin and smooth. 



Mouth. — Labrum with three teeth close together on each side of the 

 central notch: mandibles with four teeth, the fourth being small, the 

 fifth either absent or scarcely distinguishable from the inferior angle : 

 maxillae without any notch, with the two lower spines rather longer 

 than the others. Cirri : in the first pair, one ramus is only half the 

 length of the other ; in the second pair, both rami are short and about 

 equal in length ; in the posterior pairs, the segments, which are not 

 protuberant, bear four pairs of spines, of which the three lower pairs 

 are short. 



This species is widely-distributed, and where found seems 

 to be common. It is generally attached to shells of mol- 

 lusca, but I have seen it also attached to wood. I have 

 found it associated with B. tintinnabulum, var. concinnus, 

 and coccopoma, with B.psittacus, improvises and ampltitrite, 

 and with Elminius modestus. 



Young specimens bear a considerable resemblance to 

 certain young varieties of B. tintinnabulum, and can indeed 

 be distinguished from them only by a careful examination 

 of the opercular valves ; for it should be borne in mind, 

 that in certain cases the scuta in B. tintinnabulum are 

 pitted with little cavities. This species in some respects is, 

 I think, allied to B. porcatus, but it is far more closely 

 related to B. spongicola, and can be discriminated with 

 difficulty from certain varieties of this latter species. In 

 Mr. Cuming's collection, there is a group of small specimens, 

 crowded between some older specimens, which are remark- 

 able from the shell being oval in a transverse section, — 

 from the smoothness of the walls, — and from the absence 

 of pits on the scuta; yet there could be no doubt that these 

 specimens belonged to our present species. 



