Heterocuma sarsi, Miers. 615 



Vauntompsoniidas alongside of Leptocuma. Hanseii added 

 some important details to the original description, and pointed 

 out that the genus was more closely allied to the Cumidae (or 

 Bodotriida?) than to the Vauntompsoniidae, while suggesting 

 that the two families ought possibly to be united. In 

 describing H. weberi from the Malay Archipelago I pointed 

 out that, in the disposition of the thoracic exopods, the type 

 species agreed with Cumopsis among the Bodotriidaa. 

 Zimmer, in discussing the matter more recently, comes to 

 the conclusion that the known characters separating Hetero- 

 cuma from Cumopsis are not of great importance. 



Comparing Heterocuma sarsi with the type species of 

 Cumopsis (C. goodsiri) and of Vauntompsonia (V. cristata) 

 respectively, it is found to agree with that of Cumopsis in 

 the following points : — 



(1) In having the dorsal plate of the last somite not pro- 

 duced between the bases of the uropods. In Vauntompsonia 

 it is strongly produced, in Cumopsis it is transversely trun- 

 cate, while in Heterocuma it is excavated. 



(2) In having the minor flagellum of the antennules com- 

 posed of two segments. In Vauntompsonia it is unsegmented. 



(3) In having the antennal flagellum of the male composed 

 of very short segments. In Vauntompsonia they are very 

 much longer than wide. 



(4) In having a large number of branchial lobules. 



(5) In having the ischium of the second legs suppressed 

 (for Vauntompsonia see Caiman, Fisheries Ireland, Sci. 

 Invest. 1904, i. (1905) p. 16, pi. i. fig. 1). 



(6) In having unjointed exopods on the second and third 

 pairs of legs in both sexes. Vauntompsonia has fully formed 

 exopods on these limbs in the female and also on the fourth 

 in the male. 



Additional characters of less importance are found in the 

 first legs, which in Cumopsis have a group of setas on the 

 propodus apparently corresponding to the very long propodal 

 seta? in Heterocuma, and in the exopod of the uropods, which 

 has its outer edge devoid of spines in both cases. 



On the other hand, H. sarsi definitely diverges from 

 Cumopsis in the direction of Vauntompsonia only in respect 

 of two negative characters : — 



(1) The peduncle of the antennule in the male is not 

 dilated distally and carries no brush of seta?. 



(2) The endopod of the male pleopods is not produced 

 into a narrow process externally. 



In addition to these the form of the third maxilliped 

 appears to be sufficiently different to justify the separation of 

 Heterocuma from Cumopsis while not bringing it nearer to 



