670 CRUSTACEA. 



figure 9 b, at m, Plate 44. It may be made to extrude by a little pres- 

 sure, when it appears as in fig. 7i, at m', the extremity being very 

 glassy and rounded, while above it becomes very slender. It proceeds 

 from or lies in a glandular mass, which curves backward into the first 

 abdominal segment, where it meets another glassy organ, globular 

 anteriorly, but is lost posteriorly in a soft glandular mass ; it extends 

 backward towards the first pair of abdominal legs. After being 

 removed from the animal for a short time, the anterior of these glassy 

 organs loses its colour, and the fluids within contract somewhat from 

 the interior walls, as shown in figure m". The uses of this organ we 

 have not made out. We have not found it in females. It is seen a 

 little projecting in Thompson's figure of a Lucifer, and it is this pro- 

 minence which Edwards has supposed to be a rudiment of a leg of a 

 posterior obsolescent pair. 



The abdomen consists of seven oblong segments. The sixth is often 

 much longer than the fifth, and in males, at least, has frequently one 

 or two teeth, or processes,- either acute or obtuse on its inferior side. 

 The caudal segment is usually shorter than the caudal lamellse, and 

 often, instead of being straight below, in males it has a rounded protu- 

 berance ; it is furnished with two setules on the inner margin, and has 

 at apex (which is truncate) some shorter setules, with those at the 

 angles usually the longest. There are five pairs of abdominal appen- 

 dages besides the caudal pair; they have a long base and two narrow 

 multiarticulate ciliate branches, somewhat shorter than the basal 

 portion. The first of these pairs has a protuberance on the anterior 

 margin of the basal portion, which is rudely triangular in outline; it 

 has an articulation, so that it is fitted for prehension ; and its extre- 

 mity shuts upon a small spine situated on the surface of the leg. The 

 second pair has an oblong, narrow, subfalciform appendage at the apex 

 of its basal portion, in addition to the two branches. The remaining 

 three pairs have the usual form, except that the parts are very nar* 

 row; the branches are about ten-jointed. In females, all the five 

 pairs are alike in form and structure. 



The alimentary cavity is prolonged forward in the antennary seg- 

 ment, nearly to its extremity, in the form of a slender tube, like the 

 intestine. Glands, consisting of short cylindrical sacs, are clustered 

 along near the intestine, in the posterior half of the cephalothorax 

 which may be the liver; yet, as we could detect them only in females' 



