164 Annals of the South African llnscttm. 



FAMILY NANNASTACID^. 



1866. NannastacidcR, Bate, Zoological Record (for 1865), vol. ii., 



p. 329. 



1900. N., G. O. Sars, Crustacea of Norway, vol. iii., p. 79. 

 1900. iV., Rtebbing, Willey's Zoological Results, pt. 5, p. 611. 



Pseudorostral lobes with the anterolateral corners well denned ; 

 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 maxilliped usually dilated; 

 exopods on first four pairs of peraeopods 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 Nannastacus, Bate, 1865 ; Cumella, Sars, 



1865; Cumellopsis, Caiman, 1905; Platyctima, Caiman, 1905; 



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



regarded as a synonym of Xi/ii/tastucuf:, 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. suJimii, 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. tardits, 



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. a/jnatus, in which 



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



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



must be admitted as quite possible that A", reptans may be merely 



an individual variation or a phase in the life- history of A 7 , minor, 



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



Under these circumstances it seems clear that N. reptans and N. 



tardus can be safely assigned to a new genus, Paninannastacus, 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 Paranannastacidse, 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. 



