80 BALANIDiE. 



analogy, that it is more probable that the above basal 

 thickened portion of membrane is truly the basal segment 

 of the mandibles, completely continent with the labrnm ; and 

 it is, I think, not very improbable that even a large portion 

 of what in appearance belongs to the labrnm, namely, those 

 concavities to which the muscles of the mandibles are 

 attached, may, also, be part of the basal segment of the 

 mandibles. Whether or no there really are two segments 

 beneath the upper free portion of the mandibles, which have 

 become laterally confluent with other parts, I must think 

 that the square thickened piece of membrane (c 1) repre- 

 sents at least one segment. I may here observe, that 

 Prof. Milne Edwards seems to consider the mandible of the 

 higher Crustaceans as answering homologically to the haunch 

 of the leg; but, according to M. Brulle,* there ought to be 

 two basal segments (sous-maxillaire and maxillaire) bearing 

 the proper mandible, and giving rise, on the outer side, to 

 the palpus, — a structure which perfectly corresponds with 

 rny view of the mandible and palpus in Cirripedes. 



Maxilla : the point whence the long apodeme (6', PI. 20, 

 fig. 4 and fig. 7) arises, according to Audouin's views, must 

 mark an articulation, and this would separate the upper 

 free segment from the lower segments, which I believe to 

 be laterally confluent with the organs on each side. The 

 thickened membrane, of which the upper free part is formed, 

 extends a little distance beyond the insertion of the apo- 

 deme ; and this small portion beneath the point of insertion 

 may possibly answer to the square, thickened piece of 

 membrane, or second segment, supporting the mandibles. 

 Beneath it, a rather wide expanse of thin, flexible membrane 

 reaches down to the basal fold surrounding. the mouth, and 

 may thus form the third segment. 



Outer Maxilla ; the upper free segment has a spinose 

 lobe («", PI. 26, figs. 2 and 4), on its inner face, which 

 may indicate a lower and second, almost free segment. 

 Passing over this, we have, on the outside of the mouth, 

 beneath the free, upper segments, an expanse of membrane, 

 which, on the side, close to the inner maxilla?, is perforated 

 (PI. 26, fig. 4, n) by orifices which 1 believe are olfactory. 

 In some species, as in Bal. eburneus and improvisus, there 



* 'Aunalus dcs Scicnc. Nat./ 3d scries, Zoolog., torn, ii, p. 271. 



