﻿164 Annals of the South .Ifrican Museinit. 



Family .N ANN ASTACI DM. 



1M66. Nannasla('i(he, Bate, Zoological Kecord (for 1865), vol. ii., 



p. :3-29. 

 1900. .v., G. O. Sars, Crustacea of Norway, vol. iii., p. 70. 

 1000. N., Stebbing, Willey's Zoological Results, pt. 5, p. 611. 



Pseudorostral lobes with the anterolateral corners well defined ; 

 all the pedigerous segments distinct ; telson wanting ; one eye or 

 two eyes usually present ; first antenna with accessory flagellum 

 very small; second antenna of female small, indistinctly jointed; 

 mandibles normal ; terminal joint of first maxi'liped usually dilated ; 

 exopods on first four pairs of peneopods in the male, on none but 

 the first two in the female ; no pleopods in either sex ; inner branch 

 of uropods simple. 



The family includes Nannaatacus, Bate, 1865 ; Cumella, Sars, 

 1865 ; Cumellopsis, Caiman, 1905 ; Platyciuna, Caiman, 1905 ; 

 Schizotrema, Caiman, 1911 ; Diops, Paulson, 1875, being usually 

 regarded as a sj'nonyra of Nannastacus, although this can hardly be 

 justified except on the view that Paulson's description and figures 

 are misleading. With respect to the three-jointed second antennae 

 of the female he is very explicit, as also in ascribing a single filament 

 to the palp of the first maxillae. In 1911 Dr. Caiman allotted six 

 new species to Nannastacus all agreeing with N. suhinii, Sars, 1887, 

 in having no exopod on the third maxilliped of the female. He was 

 deterred from giving to this group a new generic designation by the 

 further discovery that two of the species, N. reptans and N. tardus, 

 had no exopods even on the first and second peraeopods of the 

 female. The case was complicated by the close resemblance of 

 these species respectively to N. minor and N. agnatus, in which 

 the first and second peraiopods of the female have well-developed 

 exopods, the relationship being so near that Dr. Caiman says " it 

 must be admitted as quite possible that X rrptans may be merely 

 an individual variation or a phase in the life history of X. minor, 

 and that N. tardus may stand in the same relation to N. agnatus." 

 Under these circumstances it seems clear that A^. rcptans and N. 

 tardus can be safely assigned to a new genus, Paranannastacus, in 

 which the leading character is the absence of an exopod from the 

 third maxilliped. This character they share with five other members 

 of the group, from which they would eventually be separated in a 

 family Paranannastacidu), if or when it might be established that the 

 unique feature of all the peraeopods being devoid of exopods in the 

 female was not accidental or temporary. 



