REPORT ON THE CRUSTACEA MACRTJRA. 159 



second. The posterior pair has only one long pleurobranchial plume, situated high within 

 the chamber. The branchial apparatus may therefore be arranged as in the following 

 table :— 



Pleurobrancbise, 

 Ajthrobranchise, 

 Podobranehiae, 

 Mastigobrancbise, 



h 



The plumes not only increase in number, but also in length, as they proceed 

 posteriorly. 



The fifth pair of pereiopoda has a very large coxal joint in the male, which approaches 

 nearer to that on the opposite side than in the female, and is perforated by a large foramen, 

 through which a flexile and probably erectile vas deferens projects (fig. 3o, $ ) at certain 

 periods to a very considerable extent, and rests upon the broad concave surface of the 

 first paii* of pleopoda, which in the male is narrow at the base as far as the extremity of 

 the first joint, forming a cylindrical stalk, whereas the second joint gradually thins out 

 to a hollow, spatuliform plate, probably serving to support the long and membranous 

 vas deferens in its relation to the female. 



This appendage in the male, from its formation, is of much interest, inasmuch as its 

 relation to the vas deferens shows the simplest form of the organ that in the Brachyura 

 fulfils the duties of an intromittent organ. In the present instance the smabl size of 

 the orifice in the coxa of the third pair of pereiopoda in the female precludes the idea 

 of any connection between the sexes by intromission ; but it appears certain, from the 

 great length of the extended vas deferens in some specimens after death, that the extremity 

 of the male organs are during connection brought into close proximity with the external 

 aperture of those in the female. 



On the ventral surface of the pereion of many specimens, especially females, I found 

 a layer of thin, gelatinous, and transparent material. In some places it was of thicker 

 substance, as if the centres of extending growth. Sparsely scattered through the mass 

 were stellate spicules, which consisted of branches variously radiating from a single 

 centre, forming a star with six or eight rays. Each ray slightly tapers towards the ex- 

 tremity until it bifurcates, and forms a series of small holes, varying in numbers from 

 three to six. that externally surrounds a large central hollow. 



Stereomastis auriculata, Spence Bate (PI. XVI. figs. 3, 4). 



Pentacheles auriculatus, Sp. B., Ann. and Mag. Xat. Hist., ser. 5, vol. ii. p. 280, 1S78. 

 „ auriculata on PI. XVI. 



Carapace narrow: lateral margins subparallel, armed with five teeth on the anterior 

 region, three on the median, and seven posterior to the cervical fossa. The anterior 



