616 On Heterocuma sarsi, Miers. 



Vaunlompsonia. At the same time it is quite clear from the 

 characters given above that the first two of these genera are 

 closely allied and cannot be placed in different families. 



There remains for consideration the question whether the 

 Bodotriida? and Vauntompsouiidse should not, as Hansen has 

 suggested, be merged into one family, and in this connexion 

 the characters of Heterocuma weberi are of importance. In 

 this species, of which only a male specimen is known, the 

 second and third legs bear well-developed exopods consisting 

 of an expanded peduncle and a segmented flagellum. I have 

 lately examined specimens of a closely allied species belonging 

 to the U.S. National Museum, which I hope soon to describe 

 elsewhere, which has similar exopods on these legs also in 

 the female sex. In this species, therefore (and no doubt also 

 in //. weberi), the female can hardly be distinguished from 

 a Vauntompsonia (especially if, as Zimmer suggests, Bathy- 

 cuma, which has similar third maxillipeds, is to be united 

 with Vauntompsonia), while the male only differs in having 

 no exopods on the fourth legs. Further, H. weberi has a 

 brush of setse on the antennule of the male as in Cumopsis. 

 It seems clear, therefore, that the line of separation between 

 Bodotriidse and Vauntompsouiidse can no longer be main- 

 tained. It is possible that it may even prove necessary to go 

 a step further than this. From the group formed by the 

 union of these two families it is easy to define the Leuconidse 

 by the abbreviated form of the mandible and by the possession 

 of not more than two pairs of pleopods in the male; but it is 

 not so easy to be sure that these two characters alone justify 

 the separation of the family. For the present, however, it 

 may be convenient to retain the Leuconidse as distinct, 

 although they are more closely related to the Bodotriidse 

 (sens, lat.) than to any of the remaining families of the 

 Cumacea, 



EXPLANATION OF PLATE X. 



