1973 ] 
Shear — Rhiscoso?nididae 
193 
The Mineri Group includes R. mineri , R. josephi , R. malcolmi 
and R. benedictae. In these species, the anterior coxal processes are 
usually more rodlike, not at all fused mesally, and are more or less 
sharply curved anteriad. The fimbriate or membranous areas on the 
posterior coxal processes are of limited extent, and there is an area 
on the mesal branch that appears to be glandular. The sixth segment 
of males is enlarged; the collum is white. Females have postgenital 
bodies (Fig. 3) of uncertain origin immediately posterior to the 
cyphopods. These are of limited utility in diagnosis, though they 
cannot be used to separate some species. The four species occur 
along the Oregon coast and in the foothills of the Coast Ranges. 
Certainly, by the standards that have been applied in the past, 
these two species groups might have been recognized as genera, and 
I suggested (Shear, 1972) that R. acovescor might not be congeneric 
with R. mineri. However, R. mineri, the type species of Rhiscoso- 
mides , shows a degree of intermediacy in the form of the anterior 
coxal processes, particularly when compared to R. trinitarium, which, 
in turn, is intermediate between R. mineri and R. acovescor . In the 
light of these facts, and because of the small number of species in 
the family, it seems pointless to recognize a second genus at this time. 
Key to Species of Rhiscosomides 
(excluding R. montereum) 
1 a. Sixth segment of males conspicuously enlarged (Fig. 4), lighter 
in color than other segments; anterior coxal processes of go no- 
pods usually rather rodlike (Figs. 7, 10, 15), touching mesally 
but not fused. 3 
ib. Sixth segment of males not much larger, if at all, than other 
segments; anterior coxal processes of gonopods somewhat flat- 
tened to platelike, more or less contiguous mesally, or fused. 2 
2a. Anterior coxal processes without lateral branches, fused into a 
broad plate (Fig. 17) ; Marin Co., Calif. acovescor 
2b. Anterior coxal processes with elaborate branches; Trinity Co., 
Calif trinitarium 
3a. Apical teeth or processes of anterior coxal process small, not 
directed posteriad (Figs. 7, 10, 15). 4 
3b. Anterior coxal process with large apical branch directed ventro- 
posteriad (Fig. 2) mineri 
4a. Anterior coxal processes bent sharply anteriad at nearly a right 
angle (Figs. 7, 15) 5 
4b. Anterior coxal processes long, rodlike, evenly curved (Fig. 10) 
benedictae 
