122 Mr H. Goodsir on the Genus Cuma. 



pairs of mandibles,* and two pairs of foot-jaws-t Tiiese last 

 organs will be found minutely described under Ciuna Edwardsii, 

 the species which I have been enabled to examine most mi- 

 nutely. 



The true legs may be classed into compound and simple. 

 The compound legs, as we have already stated, are four in 

 number in the genera Cuma and Bodotria ; but six in Alaima. 

 The first, or compound legs, are divided into two parts, the 

 anterior or ambulatory, and the posterior or natatory. The 

 simple legs are much shorter than the compound, and are 

 more adapted for prehension ; but they ai'e unarmed with 

 claws, and are seldom used for this purpose. 



The abdomen is moniliform, seven jointed, in all the genera. 

 The last joint is very small in the genera Cuma and Bodotria ; 

 but in Alauna we find this segment very much developed. 

 All the genera have the sixth abdominal segment armed with 

 a pair of long bifurcated styles. The genera Cuma and 

 Alauna are quite free of appendages to the other abdominal 

 segments ; but in Bodotria we find that all the abdominal 

 segments are armed with a pair of bifurcated appendages. + 



Owing to the opacity of the shell, I have not been able as 

 yet to make out the minuter parts of the anatomy of these 

 animals. The intestinal canal consists of a long straight tube, 

 considerably dilated as it passes through the thoracic portion 

 of the body ; when it reaches the abdominal portion it sud- 

 denly becomes much narrower. 



The anal aperture is found in the seventh abdominal seg- 

 ment. 



The branchiae§ are situated on each side of the thorax, 

 immediately above the insertions of the legs, and approach, 

 in their comb-like appearance, to those of the higher Crus- 

 tacea. Interiorly, each of them is connected with the su- 

 perior foot-jaws, and excepting that connection, lies appa- 

 rently quite free in a sac formed by the reflection of a thin 

 transparent membrane, which lines the internal surface of 

 the thorax. The superior part of the branchias consists^of 

 one continuous piece, which is bent in a hook-like manner at 

 its posterior extremity ; the branchia? themselves arise from 



PI. II. Figs. 3, 4, 5. t PI. II. Fig. 7. } I'l. II. Fi-. 17- § PI. IV. Fig. 11. 



