42 LEPADIDvE. 



down nearly parallel to the thin, outer, flexible membrane 

 of the mouth, is attached to the corium, and thus serves as 

 a support to the whole organ. This apodeme is embedded 

 in muscles (PI. X, fig. 1 0) ; there are other large muscles 

 attached to the inner side of the organ, and again others 

 running laterally towards the mandibles. The apodeme, 

 of course, is moulted with the integuments of the mouth. 

 The Outer Maxillce (PL X, figs. 16, 17) serve as a lower 

 lip; they are thicker than the other trophi; they have 

 their inner surfaces clothed with spines, sometimes divided 

 into an upper and lower group, and occasionally separated 

 by a deep notch : there are often long bristles outside. 

 They are furnished with at least two muscles ; in sessile 

 Cirripedes I have seen that they are capable of a rapid 

 to and fro movement, and I have no doubt that their 

 function is to brush any small creature, caught by the 

 cirri, towards the maxillae, which are well adapted to aid 

 in securing the prey, and to hand it over to the mandibles, 

 by them to be forced down the oesophagus. On the ex- 

 terior face of the outer maxillae, above a trace of an upper 

 articulation, either two small orifices or two large tubular 

 projections can always be discovered ; and these, as will 

 presently be mentioned, I believe to be olfactory organs. 

 Cirri. — The five posterior pair are seated close to each 

 other and equidistant ; the first pair is generally seated at a 

 little distance, and sometimes at a considerable distance 

 from the second pair. The first pair is the shortest ; the 

 others, proceeding backwards, increase gradually in length. 

 The rami of each pair are either equal in length or slightly 

 unequal: those of the first pair are oftenest unequal. 

 The number of segments in the posterior cirri is some- 

 times very great ; in one species of Alepas, there were 

 above sixty segments in one ramus, the other ramus being 

 in this unique case (PI. X, fig. 28) small and rudimentary. 

 The pedicels consist of two segments, a lower, longer, and 

 upper short one (fig. 18, c, d.) In the usual arrangement 

 of the spines on the segments of the three posterior pair 

 of cirri, there are (figs. 26, 27) from three to six pair of 



