92 
Psyche 
[September 
Gonopod Anatomy of Rhiscosomides Species 
The gonopods of Rhiscosomides species males conform well to the 
striarioid pattern. The sternum (Fig. 2 , S) is heavily sclerotized 
and anteriorly margined, with deeply depressed openings from the 
tracheal spiracles. Laterally, the sternum is broadly expanded, con- 
cealing the bases of the coxal processes. The anterior coxal processes 
(Fig. i, AC) are closely appressed, and in the Acovescor Group 
of species are wholly or partially fused to form a broad plate. A 
strong lateral branch is usually present (Fig. 2 , LB), but may be 
a broad flange (Fig. 7), or the largest part of the process (Fig. 18). 
The length of the anterior coxal process and the form of its terminal 
branches are of excellent taxonomic and diagnostic value. The pos- 
terior coxal process usually has three branches: the anterior branch 
(Fig. 7, AB), the mesal branch (Fig. 7, MB), usually the largest, 
and fhe generally much smaller posterior branch (Fig. 7, PB). The 
mesal and posterior branches are usually connected by a membranous 
or fimbriate area. There is also a flabelliform median structure 
arising from the heavily sclerotized part of the sternum that extends 
between the gonopods. This sternal flap (Fig. 10, SF) usually 
comes off with one or the other of the gonopods when they are sep- 
arated. The telopodites (Figs. 2, 10, T) are amorphous, lobelike 
structures that are usually displaced laterally, but may interlock 
basally with the lateral extensions of the sternum or of the anterior 
coxal processes. They are of little taxonomic value. The posterior 
gonopods are rather uniform throughout the genus (Figs. 9, 14, 16). 
In my 1972 description, I erred in calling the narrow anterior mesal 
coxal lobe the telopodite. The actual telopodite is flattened and 
irregular in outline and bears a more or less pointed process on the 
posteriomesal margin, which extends posteriad. This telopodite pro- 
cess and the coxal lobe protect and partially support the anterior 
gonopods, and in some animals, clasp between them the coxae of 
legs 10. 
In terms of gonopod anatomy and a few other characters, the six 
species known from males fall into two groups. In the Acovescor 
Group ( R . acovescor, R. trinit ariurn) , the anterior coxal processes 
tend to be fused or broadly contiguous mesally, and are rather short. 
Areas of highly branched, fine cuticular fibers are well developed on 
the posterior coxal processes. The sixth segment of the males is only 
slightly or not at all enlarged ; in R. acovescor the collum is colored 
like the other segments, instead of being white. Females have not 
been collected. Both species occur in California, and R. montereum 
will probably also prove to belong to the group. 
