Annelids of Alaska— HARTMAN 
17 
Spinther alaskensis new species 
Fig. 1 a-c, 2 g-j. 
Collections. Stations 51-40 (1); 66-40 (2). 
The largest individual measures 28 mm. long 
and 20 mm. wide. Number of segments is 46 
or 47. The first two segments, preceding the 
prostomium, and the last six or seven, following 
the pygidium, are short and incomplete mid- 
dorsally. The dorsum is slightly arched and 
nearly uniformly covered with notopodial ridges 
except for a narrow, median, longitudinal stripe 
(Fig. 1 a). The ventrum is flat and solelike; 
it is more or less completely covered with seg- 
mentally arranged rows of spherical papillae, 
strewn thickly over the neuropodial bases and 
less so medially; the segmental intervals are 
smooth. A broad, median region has similar 
papillae but much sparser and irregularly dis¬ 
persed. 
The prostomial appendage is a spherical 
(Fig. la) (station 66-40) or elongate (station 
51-40) papillar lobe. The prostomium is low 
and has two pairs of large, oval, reddish-brown 
eyespots, located in the groove where the lobe 
and body join; the anterior eyes are the larger 
but the two of a side nearly merge with each 
other. 
The notopodial ridges (dorsal lamellae) have 
wavy fore and hind margins; the waves cor¬ 
respond in their distribution with that of the 
setal fascicles, the concavity lacks setae, the con¬ 
vexity has them. The anterior and posterior 
margins of the lamellae are about equally de¬ 
veloped. The first two pairs of notopodia, in 
front of the prostomium, are directed forward 
(Fig. l a); the third pair is in line with the 
prostomium and farther back they are lateral in 
position. The most posterior are directed back 
so as to surround the anal region. The noto¬ 
podial setae are arranged in alternating series 
(Fig. 1 b) along the membranous margins of 
the ridges. In median parapodia, where they 
have their maximum development, there are 
about 16 sets of setal fascicles in a notopodium; 
they consist of eight sets in the anterior margin 
and alternate with the same number of sets in 
the posterior margin. Each set consists of a 
fan-shaped fascicle of about nine setae, but 
some setae are embedded and visible only by dis¬ 
section. The total number of setae in a ridge 
approximates 140 to 200. The symmetry of this 
pattern on a well-preserved individual is a 
striking feature and may signify a unique struc¬ 
tural character in the functioning of the in¬ 
dividual, perhaps to aid the flow of water 
forward and back. 
Notopodial setae are of two kinds (Fig. 2 
h-j). They consist of thick, bluntly pointed, 
straight, acicular spines numbering eight to 
ten in each fan-shaped fascicle and a few, very 
slender, delicate rods that are slightly curved and 
distally bifid (Fig. 2 i). The thickness of the 
latter is only one-fourth to one-sixth that of the 
larger spines; they are thus easily overlooked. 
Neuropodia are long and thick; they taper 
distally and are provided with a thick, conical, 
superior lobe (Fig. 1 c) that is somewhat post- 
setal in position. Their bases are strongly 
wrinkled as though capable of great lateral ex¬ 
tension, and the ventral side is covered with 
spherical papillae that resemble those on the 
ventral side of the body. One, seldom two, large 
composite, yellow hooks project from the distal 
end of the neuropodium. These large hooks are 
flat and knifelike; their appendage is strongly 
curved. The distal end of the shaft, at its longest 
part, is weakly trilobed (Fig. 2 g). The em¬ 
bedded part of the setal bundle, by dissection, 
is seen to consist of several developing, com¬ 
posite hooks, in various stages of growth; they 
are surrounded by an enveloping acicular 
bundle. The acicula are long, slender, tapering, 
pale rods (Fig. 1 c). 
The proboscis, partly everted in one in¬ 
dividual, but observed also by dissection, is a 
soft, voluminous, rosette-shaped sack, as is 
typical of the genus. 
S. alaskensis belongs to the group of species 
in which the ventrum is papillose. It has noto¬ 
podial setae with tips that are both entire and 
bifid. To this group belong also S. citrina 
