Alaskan Ascidians — A bbott 
139 
FIG. 1. Chelyosoma macleayanum. Dorsal view of 
disc; growth lines indicated only on intersiphonal 
plate and two siphonal plates, a, Individual with 7 
marginal plates; b, individual with 8 marginal plates. 
embryos and immature larvae within the atrial 
cavity. 
The tentacle counts for the 4 largest speci- 
mens (Table 2) are higher than those usually 
obtained in A. callosa, although Arnback ( 1934: 
53) records similar numbers. The difference 
here is probably not significant. Tentacle counts 
vary a good deal depending on the degree of 
development of a fourth cycle of very small 
tentacles; in the present study these tentacles 
were counted when present, whereas earlier 
workers have often ignored or overlooked them 
in making counts. 
The specimen from 74 1 ft. (123 fathoms) 
represents an unusual depth record for the 
species; Van Name (1945: 180) indicates a 
maximum depth for A. callosa of about 80 
fathoms. 
DISTRIBUTION: Norway, N. Ireland (?), the 
Faeroes, Iceland, Greenland, eastern N. America 
south to Cape Cod, arctic N. America, western 
N. America south to Puget Sound, Bering Sea, 
and Korea. 
family RHODOSOMATIDAE 
Chelyosoma macleayanum Broderip & Sowerby, 
1830 
Fig. la, b 
Chelyosoma macleayanum Huntsman, 1921, 
pp. 27-33, pi. 1, fig. 1, text fig. 1; Hart- 
meyer, 1924, pp. 2-9, text fig. 36; Arn- 
back, 1934, pp. 76-84, pi. 5, figs. 27-33; 
Van Name, 1945, pp. 205-207, text fig. 
118. 
DESCRIPTION : The following notes supple- 
ment the description of Van Name (1945). 
Dorsal disc of test divided into plates arranged 
as follows: 6 triangular plates forming a ring 
about each aperture; remainder of disc bearing 
1 central intersiphonal plate and 7 or 8 mar- 
ginal plates, the 8th marginal plate, when pres- 
ent, occupying an asymmetric position to the 
right of the center of the intersiphonal plate 
( Fig. 1 ) ; lateroventral plates below rim of disc 
TABLE 2 
Ascidia callosa 
STATION 
NUMBER 
DIMENSIONS 
( mm.) 
ORAL 
LOBES 
ATRIAL 
LOBES 
TENTA- 
CLES 
INTERI 
Right 
'sfAL LONGITl 
VESSELS 
Left 
JDINAL 
Total 
20 
11X 6X 1* 
8 
32 
19-20 
16 
35-36 
27 
I4x 9X 4 
8 
6 
24 
20 
26 
19 
14 
33 
42 
14X10X 4 
8 
6 
61 
16X16X 5 
7 
6 
7 Of 
20 
16 
36 
32 
33X24X12 
7 
6 
ca. 50 
18 
16 
34 
42 
41X28X13 
6 
6 
ca. 65 
17-18 
19 
36-37 
44 
75X53X35 
ca. 55 
26 
23 
49 
* Measured on animal removed from tunic; all other size measurements in table made on intact animal in tunic, 
t Fourth order tentacles unusually numerous. 
