Alaskan Ascidians- — Abbott 
141 
TABLE 4 
Chelyosoma macleayanum , PER CENT OF POPULATION Bearing SPECIFIC Numbers OF 
Marginal Plates 
REFERENCE AND LOCATION 
NUMBER OF 
SPECIMENS 
EXAMINED 
NUMBER OF MARGINAL PLATES 
5 
6 
7 
8 
9 
Uncertain 
% 
% 
% 
% 
% 
% 
Hartmeyer, 1924; material mostly from 
Greenland 
53 
2 
9 
79 
2 
0 
8 
Present collections; Point Barrow, Alaska 
15 
0 
0 
33 
67 
0 
0 
Arnback, 1934; material from Siberian arctic. 
mostly Pitlekaj 
185 
0 
0 
11 
87 
2 
0 
each siphonal plate and numerous papillae dor- 
sally and dorsolaterally to which mantle muscles 
attach. Mantle thin, with muscles strongly de- 
veloped about the siphons and below the mar- 
ginal ridge of the disc but nearly absent else- 
where. Tentacles simple, of 2-4 orders (Table 
5). Dorsal tubercle with a crescentic slit (Fig. 
3 c); 20-40 dorsal languets of 1 or 2 sizes 
(Fig. 3 c; Table 5). Pharynx relatively complex 
and thick-walled (Fig. 3 d)\ 18-31 internal 
longitudinal vessels on each side, often inter- 
rupted, where incomplete their position being 
marked by papillae; transverse vessels irregularly 
branched, in places forming a perforated sheet 
medial to the stigmata; stigmata scattered, vary- 
ing from oval slits to spiral infundibula, ex- 
hibiting complex anastomoses with other phar- 
yngeal structures; external pharyngeal wall in 
places provided with branching bundles of mus- 
cle fibers. Anal margin lobulate (Fig. 3e) . 
Gonads situated in the intestinal loop and rami- 
fied over most of the inner and outer surfaces 
of the intestine. 
DISCUSSION: This remarkable species is 
known with fair certainty only from Redikor- 
zev’s original material (7 specimens, Sea of Ok- 
hotsk) and from 3 small individuals from 
Teller and Point Hope, Alaska, reported by Van 
Name (1945). It differs from all other mem- 
bers of the genus in lacking a clear series of 
dorsal plates arranged with fair geometrical reg- 
ularity and precision, the test instead being 
relatively smooth or dotted with scattered thick- 
enings and protuberances. The latter are espe- 
cially well developed in the present specimens, 
and, while irregular, do sometimes suggest a 
crude pattern consisting of a central intersi- 
phonal plate (divided in the median sagittal 
TABLE 5 
Chelyosoma inaequale 
STATION 
DIMENSIONS OF TEST 
(mm.) 
NUMBER OF 
DORSAL 
LAN- 
INTERNAL LONGI- 
TUDINAL VESSELS 
NUMBER 
L 
W 
Ht 
TENTACLES 
GUETS 
Right 
Left 
26 
20 
10 
19 
ca. 36 of 1st 2 orders; ca. 39 
of 3rd and 4th orders 
22, of 
2 sizes 
19 
18 
44 
25 
16 
20 
ca. 58 of 1st 2 orders; ca. 55 
of 3rd order; 4th order very 
small, numerous, and ir- 
regularly placed 
20 
19 
19 
27 
45 
35 
18 
ca. 58 of 1st 2 orders; few 
scattered smaller tentacles 
40 
28-31 
20-22 
