Danielssenia sibirica Group — Wilson 
elongate-oval structure centralized above cross- 
wise sclerotization ; leg 6 a single seta arising 
from prominent lobe at each side of genital 
field. Other urosome segments ventrally with 
distal rows of spinules consisting of lateral 
groups of stout spinules and a more slender 
medial group irregular in length, as partially 
shown in Figure 1 B; anal segment deeply cleft 
in middle; row of spinules overlying bases of 
caudal rami. Caudal ramus (Fig. 1 B) a little 
longer than outer margin of anal segment 
(about 1:0.76) and its own greatest width at 
base (about 1:0.88); with lateral and apical 
groups of spinules; dorsal seta near middle; 
other caudal setae placed apically or subapically: 
the two outer marginal setae of similar length 
to one another and to ramus, the proximal sub- 
apical, the distal seta apical; two stout apical 
spinulose setae, jointed near bases, the middle 
about twice length of outer seta and less than 
that of urosome; innermost apical seta little 
shorter than lateral setae. Rostrum (Fig. 1 A) 
nearly twice as long as wide, nearly equaling 
length of proximal three segments of anten- 
nule; apex truncate; base not demarcated from 
cephalosome. (Habitus characters agree with 
the few given by Willey, except that he de- 
scribes the rostrum as "defined behind.’’) 
Antennule (Fig. 1 G). First 4 segments of 
similar width, proximal 3 subequal in length 
to one another, the fourth reduced to half their 
length; last 2 segments reduced in width, the 
sixth narrower and longer than fifth (Willey 
gives their length as identical). Aesthetes of 
segments 4 and 6 arise on common base with 
a slender seta. Number of setae and aesthetes: 
Segment 1 2 3 4 5 6 
Setae 1 8 6 4 8 6 
Aesthetes 1 1 
Segments 2 and 6 bear 1 seta, and segment 5 
bears 3 stout, modified setae, armed with large 
spicules and tipped with hairlike setules. Other 
setae are plumose or naked as shown in figure. 
Antenna (Figs. lJ-K). Allobasis with 1 long 
marginal seta reaching to about middle of apical 
segment (endopod). Exopod segment 1 with 2, 
segment 2 with 1 and segment 3 with 1 lateral 
and 2 apical setae (presence of 2 setae on seg- 
ment 1 distinguishes sibirica group in part 
439 
from other species of the genus). Distal endo- 
pod segment (Fig. 1 K) with marginal group of 
2 stout spines and longer modified seta similar 
to apical "geniculate” setae (this seta is the one 
referred to by Willey as ‘'long curved claw”) ; 
apically, 6 elements consisting of 1 stout spine, 
3 modified "geniculate” setae, a longer sparsely 
plumose seta, and a short, slender seta placed 
subapically (this latter seta omitted by Willey). 
Mandible. Gnathal blade (Fig. lL) with 5 
bifurcate denticles, a single denticle, and a stout 
subapical spiniform seta. Palp (Fig. 1 H) : Basis 
with 4 setae; endopod unsegmented with 3 
lateral and 4 apical setae; exopod 2-segmented, 
bearing 2 and 3 setae respectively. 
Maxillule (Fig. 1 D ; "maxilla” of Willey of 
which only exopod setae were mentioned in 
text). Gnathal lobe prominently produced, 
bearing 2 surface setae and 10 stout apical 
spines. Coxa and basis not separated, bearing 
2 elongated laciniae, the first with 5 apical 
setae, the second (representing the basis) with 
2 lateral and 4 apical setae, one a stout spine. 
Endopod and exopod unsegmented, each with 
3 setae; those of exopod the longest of entire 
appendage. 
Maxilla (Fig. 1 1; not described by Willey). 
With 4 stout, well-defined endites; number of 
setae and modified spines from proximal to 
distal endite: 3,2, 3, 3. Endopod distinct with 2 
long slender setae. 
Maxilliped (Figs. lE-F) . Essentially as fig- 
ured by Willey, except that accessory seta of 
claw arises near base rather than near apex 
(Fig. 1 E). (Willey’s figure, copied by Lang 
(1948), shows only the apex of the seta which 
makes it appear very short and as arising be- 
yond the middle of the claw, as Sars (1898) 
has also, probably incorrectly, shown it for D. 
sibirica . ) 
Legs 1-4 (Figs. 2 A-D). Endopod of leg 1 
reaching to end of or little beyond exopod; 
that of leg 2 reaching end of exopod, progres- 
sively shorter in legs 3 and 4, so that in leg 4 
it reaches to only a little beyond exopod seg- 
ment 2. Outer distal edge of endopod segments 
1 and 2 produced in legs 2-4, most pronounced 
in segment 2 of leg 3 (as noted and figured by 
Willey). Apical setae of exopods and endopods 
of legs 2-4 somewhat spiniform, inner setae 
