394 PROCEEDINGS OF THE NATIONAL MUSEUM yoL. 113 
fonticola, P. feuerborni, and P. vicesema. Exp. P.3 of the male is very 
strong and modified, and appears to be 3-jointed. A subgenus should 
probably be established on the basis of the characteristic form of Exp. 
P.3 male; this would probably be more striking than the present 
division based on Enp. P.4. Unfortunately, however, the males 
of many species are still unknown. It is interesting that the structure 
of Exp. P.4 is very different in the two new species. 
Because many species of the genus Parastenocaris have been 
described on the basis of only one sex, and not infrequently from a 
single specimen, comparison of the two new species with those already 
described is very difficult, and it is impossible to determine the range 
of variation in the different characters. 
In Lang’s (1948) keys for the determination of the species of Para- 
stenocaris, the female P. brasilibathynellae runs to P. hexacantha, while 
the male comes to P. brevipes and P. feuerborni. P. brasilibathynellae 
is so different from the other species that it is not likely to be easily 
confused. It is not possible to place this species correctly in the key 
of Chappuis (1958a), which is based on the form of Enp. P.4 male. 
The sexual dimorphism of the furca is very important, and in the 
Harpacticoidea two types generally can be distinguished: 
Mensural differences, of which examples occur in Eucanuella spinifera (female 
with shortened furea), Porcellidiwm viride (female furea much longer), Para- 
camptus schmeili (female furca secondarily lengthened), and Schizopera minuta 
(female furca secondarily lengthened). 
Fundamental differences in characters, of which examples occur in Paraphyllo- 
podopsyllus intermedius, Attheyella crassa, Huntemannia judensis, Parastenocaris 
trisaetosa, and P. brasilibathynellae. 
In species of the latter group, it is evident that it is the female furca 
that is modified. In the first group of species, although the di- 
morphism is more superficial, it is also clear from comparison with 
their nearest relatives that the female furca may be associated with a 
function of producing sexually attractive substances. Such sub- 
stances would be very important to animals living in the subterranean 
interstitial system. 
As mentioned above, Lang’s key leads to P. hexacantha Kiefer 
(1936), which has a furea similar to that of P. brasilibathynellae. 
Unfortunately, the male of P. hexancantha is unknown, but we may 
conclude that a similar sexual dimorphism exists. The A.1 of P. 
hexacantha suggests that of P. brasilibathynellae, especially in the 
position of the two sensory setae, and the thoracic limbs have some 
features in common. We can, perhaps, consider P. heracantha, from 
the Rio Serido, Brazil, as the surface form of P. brasilibathynellae, 
and P. trisaetosa Chappuis (1954b) from Madagascar may be a sub- 
terranean analogue. 
