Charadracarus n. gen. — N ewell 
165 
Charadracarus hurdi new species 
FEMALE: Idiosoma of holotype 711 ji long, 
459 /x wide, length/width 1.54. Scutum of essen- 
tially same form as found in C. delitescens, but 
sensilla not fusiform. Swollen distal portion with 
a number of small refractile points, and only a 
vestige of the shaft at the tip. Prosensillar setae 
considerably longer than the others. Setae ap- 
pearing barbed at high magnifications, but rela- 
tively smooth at magnifications of 150X or 
lower. Posterior margin of plate rather deeply 
notched, and immediately anterior to the notch 
is a weakly defined, short, narrow crista. Cuticle 
faintly pigmented, yellow-brown in color. Ocular 
plates totally absent. Dorsal propodosomal setae 
of two series, major and minor, the major setae 
larger than the minor, but otherwise not differ- 
ing in form (Figs. 29, 30). The tips taper uni- 
formly to a very fine point, and are not expanded 
or tufted as in C. delitescens (Fig. 45). Seti- 
gerous sclerites very minute and difficult to ob- 
serve. Coxa I with eight barbed setae each, 
supracoxal setae absent; coxal ring slightly open 
dorsally. Coxa II with seven or eight setae. Pars 
medialis coxae and intercoxal area as in Chara- 
dracarus delitescens. Coxae III and IV with six 
to eight setae each, usually eight. No trace of 
either apodemes or Ldssenia- organ in mem- 
branous cuticle between II and III. 
Base of gnathosoma and rostrum essentially 
as in C. delitescens . Chelicerae not in favorable 
position for study, but with only three feebly 
developed teeth behind the tip. Dorsal mem- 
brane well developed, slightly longer than one- 
half the length of the tarsus. Palpi with five 
free segments, trochanter with no indication of 
a fenestra on anterior surface. Femur with one 
seta dorsally and three setae on posterior mar- 
gin, patella with two dorsal setae, tibia with six 
setae plus the terminal odontus (Figs. 2, 7). 
Tarsus with a solenidion very near the base of 
the segment plus seven setae more distally 
located. Of these, the two distidorsal ones are 
the heaviest and shortest, and are also smooth. 
The distal one of these two setae is typically 
eupathidiform with a distinct central canal 
and a moderately thick wall. Its homologue in 
C. delitescens is solid in several specimens ex- 
amined by the writer. In the present species, the 
more proximal of these two setae is solid, with- 
out a central canal. The tip of the palpal tarsus 
is drawn out into a fingerlike projection. 
Femora I and II divided, III and IV undivided. 
Eupathidia confined to tarsi; vestigial setae ab- 
sent. Tarsus I with a single si at 0.72-0.74; 
usually with one or two s 2 between 0.56 and 
0.65, one on anterior and one on posterior as- 
pect of tarsus. Famulusi at 0.82. Approximately 
16 or more eupathidia between 0 . 53 - 0 . 57 ^ and 
0.72-0.77^. Tarsus II with a single s 2 at 0.54- 
0.55, f 2 at 0.46-0.47, and a single eupathid at 
0.88p. Tarsi III and IV each with a single S 3 at 
0.12-0.32, the basal position probably more 
common. Remaining chaetotaxy essentially as 
in C. delitescens. Special features common to the 
two species are the slightly acuminate tips of 
s 2 and the apparently consistent difference in 
size of the dorsal solenidia of tibia IV (Figs. 
27,37). 
type locality: Point Barrow, Alaska, col- 
lected by Paul Hurd, Jr. 
REMARKS: This species is very similar to 
C. delitescens new species, and to C. grandjeani 
(Andre). The most significant differences are in 
the form of the sensilla, and the difference in 
structure of major setae of the dorsal and mar- 
ginal surfaces of the hysterosoma. The difference 
in form of the distal member of the group of 
two dorsal eupathidia at the end of the palpal 
tarsus differentiates C. hurdi from C. delitescens. 
This difference is especially significant since it 
shows that the scimitar-like setae found in this 
position in certain Johnstonianidae are modified 
eupathidia. Examples of this are found in the 
larva of Centrotromhidium distans (Newell 
1957: 418, figs. 28, 29, 30), Johnstoniana lati- 
scuta (Newell 1957: 431, fig. 92), and others. 
Charadracarus delitescens new species 
FEMALE: Body (Fig. 31) 513 to 711 \x long 
to tip of scutal spine, 270 to 351 /x wide, length/ 
width 1.87 to 2.02; average 628 n by 324 /x, 
length/width 1.94 (4 specimens). Sensilla of 
scutum (Fig. 36) with a fusiform swelling near 
the middle, this swelling bearing a few minute 
spines. Basal half of sensillum appearing faintly 
roughened, and under oil immersion a number 
of delicate barbs are visible (Fig. 83). Directly 
anterior to the sensilla are the prosensilla, 
slightly longer than the other setae. In addition, 
