Heterocumn sarsi, Miers. 015 



Vauntompsoniiila; alongside of Leptocuma. Hansen added 

 some iinpoitant details to the ori;;iii!il dt'sciiptioii, and pointed 

 out that the ^'enu.s was more ch)Hi'ly aliie<l to tiie (Jumidie (or 

 Budotriidiv) than to the Vaunioinpsoniidae, while su^^gesting 

 that the two funiilies ought possibly to bo united. In 

 describing //. weberi from the Malay Archipelago I pointed 

 out that, in the disj)osition ot" the thoracic exopods, the type 

 species agreed with Cumopsis among the Bodotriida?. 

 Zimmer, in discussing the matter more recently, comes to 

 the conclu-^ion that the known characters separating lletero- 

 cuma from Cumopsis are not of great importance. 



Comparing Ife(erocnm'i sarsi with the type species of 

 Cumopsis {C. good.siri) and of Vauntompsonia {V. cristata) 

 respectively, it is found to agree with that of Cumoj>sis in 

 the following jioints : — 



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

 duced between the bases of the uropods. In Vuuntompsonia 

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

 cate, while in Ifelerociima it is excavated. 



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

 posed of two segments. In Vduntompsonia it is uiisegmented. 



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

 of very short segments. In Vauntompsonia they are very 

 much longer than wide. 



(•i) 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, whicii in Cumopsis have a group of setaj on the 

 propodus aj)parently corresponding to the very long propodal 

 sela? in Ileterocuma, and in the exopod of the uropods, which 

 has its outer edge devoid of spines in both cases. 



On the other hand, //. 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 maxillij>ed 

 appears to be sufficiently different to justify the separation of 

 Ileterocuma from Cumopsis while not bringing it nearer to 



