26 GL O. Sars. 



behind by a deep notch, giving the head, in a lateral view 

 of the animal, a physiognomy rather different from that in 

 M- australiens is. 



In the form and structure of the shell, scarcely any 

 essential difference is to be found from that in the said 

 species, excepting that perhaps the inferior edges of the 

 valves are more densely setiferous. 



The eye is comparatively larger than in M. australiensis, 

 almost completely filling up the frontal part of the head, 

 and the crystalline bodies seem also to be more numerous. 



The antennulæ (fig. 3) are distinguished by their 

 unusual length, being comparatively nearly twice as long as 

 in the preceding species. They are very narrow, sublinear 

 in form, and provided behind with scattered, delicate hairs. 

 The sensory bristle of the anterior edge occurs much nearer 

 to the base than to the tip, being placed at about the end 

 of the first third part of the length of the antennula. 



The antennæ do not exhibit any essential difference 

 from those in the preceding species; the 1st pair of legs 

 (fig. 4) too are constructed in the very same manner, the 

 subapical seta being, as in that species, quite simple. 



The tail (fig. 5) likewise looks rather similar. But, on 

 a closer examination, the terminal claws are found to differ 

 essentially in being each provided at the base with a well- 

 marked, comb-like series of secondary teeth (see fig. 6). 



A similar armature, as is well known, is found in 

 M. brachiata, whereas in the other European species, M. 

 paradoxa, the claws are quite smooth, as in M. australiensis 

 and M. propinqva. 



The ephippium (fig. 7), as in the preceding species, 

 always contains 2 egg-amp ullæ, which in this form, however, 

 are placed more transversely, or in a manner similar to that 



