38 
PACIFIC SCIENCE, Vol. II, January, 1948 
ten. All hooks are clearly bidentate at their 
distal end, the notopodial (Fig. 10 d) some¬ 
what finer than the neuropodial (Fig. 10 c) 
ones. The tube is fragile, dark, and cindery; it 
is irregular in shape and occupies crevices of 
serpulid tubes. 
T. hamatus is characterized in having some 
segments with both notopodia and neuropodia 
provided with bidentate hooks; tentacular cirri 
originate immediately above the notopodial 
ridge. Three other species of Tharyx have been 
described from the northern Pacific region; 
they are T. multi fills Moore (1909: 267) and 
Fig. 10. Tharyx hamatus new species (station 108- 
40) : a, anterior end in left lateral view, X 35; 
h, posterior neuropodium showing distal ends of neuro- 
setae, X 105; c, neuroseta from the same parapodium, 
X 1125; d, two notosetae from the same parapodium, 
X 1125; e, distal end of a pointed notoseta, X 1125. 
T. gracilis Moore (1923: 187) from California, 
and T. parvus Berkeley (1929: 307) from 
British Columbia. The first and third of these 
species have only pointed setae in notopodia 
and neuropodia; T. gracilis has pointed setae in 
notopodia and blunt spines in neuropodia. 
T. hamatus differs from all of these most clearly 
in that parapodia have bidentate hooks in some 
segments. 
Holotype in the U. S. National Museum. 
Type locality. Alitak Bay, Alaska, shore. 
Distribution. Alaska. 
Genus Acrocirrus Grube 
This is a small genus, characterized by the 
presence of composite neuropodial hooks. The 
anterior end is provided with a pair of thick, 
grooved palpi and a few pairs of tentacular 
cirri. Notopodial setae are simple, slender, and 
distally pointed. Color of the body is usually 
dark. 
Seven species have been described in the 
genus; five originate in the north Pacific. They 
are (1) A. crassiftlis (Moore, 1923: 188) from 
southern California, (2) A. heterochaetus An¬ 
nenkova (1934: 326) from Bering and Japan 
seas, (3) A. muroranensis Okuda (1934: 202) 
from Japan, (4) A. uchidai Okuda (1934: 
197) from Japan, and (5) A. validus Maren- 
zeller (1879: 148) from Japan. Among these, 
only one, A. heterochaetus, is known to have 
the eleventh segment modified and provided 
with heavy, simple hooks; it agrees therein with 
the type of the genus, A. frontifilis Grube (see 
Fauvel, 1927: 104) from the Mediterranean 
Sea. 
Acrocirrus heterochaetus Annenkova 
Fig. 11, a-c. 
Acrocirrus heterochaetus Annenkova, 1934: 
326-327, fig. 7 [in Russian]. 
Collections. 20-40 to 22-40 (1); 24-40 
(1) . 
The color (preserved) is dark slaty brown; 
there is no pigment pattern. The prostomium is 
