46 
TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
give me his opinion, whether it was really the same species as that described by 
him as Sterech. margaritaceus , pointing out for him certain minor differences 
between the two forms. Prof. DöDERLEIN kindly told me that, in spite of these 
differences, it was certainly identical with the species described by him. Thus, 
through the direct comparison with the specimen from the »Hassler» as well as with 
those described by DöDERLEIN, it is made evident that the specimens before me 
really belong to the species called margaritaceus by these authors. 
DöDERLEIN points out (Op. cit. p. 219) the following main characters as distin- 
guishing this species from the other species of the genus Sterechinus: The height 
of the test is lower than half the horizontal diameter; all the ocular plates are con- 
stantly excluded from the anal area; the blade of the globiferous pedicellariæ is 
almost quite open. — The rather considerable material of the species procured by 
the Swedish Southpolar Expedition, however, necessitates some modifications of 
these characters of the species. 
As shown by the following measurements of the specimens in hand, the height 
of the test is, in the larger specimens, generally lower than half the diameter; in 
one specimen, however, of 54 mm. diameter the height is 30 mm., thus not in- 
considerably higher than half the diameter. Likewise in the small specimen of 
Largest width of 
Number of plates. 
Dia- 
meter. 
Peri- 
stome. 
Apical 
area. 
Anal 
area. 
Longest 
spines. 
Station. 
Height. 
Ambu- 
lacra. 
Inter- 
ambu- 
lacra. 
Ambu- 
lacra. 
Inter- 
ambu- 
lacra. 
Ocular plates. 
mm. 
mm. 
mm. 
mm. 
mm. 
mm. 
mm. 
mm. 
St. 16 
60 
25 
13 
12 
7 
12 
23 
38 
19 
II nearly in( 
) contact ) 
ca. 20 
> 
60 
26 
14 
13 
6.5 
12.5 
23-5 
38-39 
20 — 21 
I in contact 
C£. 20 
I I and V I 
St. 20 
58 * 
26 
15 
13 
8 
13 
22 
33-34 
18 
; in wide 
1 contact f 
? 
56 
24 
h 
h . 5 
6 
12 
21.5 
38-39 
19 
all excluded 
t 
» 
54 
25 
13 
h. 5 
6 
12 
22 
37 
19 
all excl. 
ca. 19 
St. 59 
54 
30 
• 5-5 
ii. 5 
6 
12 
20.5 
35 
18 
all excl. 
? 
St. 16 (?) 
52 
23 
13 
10 
5.2 
12 
20.5 
35 
18—19 
all excl. 
? 
» 
52 
23 
13 
10.5 
6 
II 5 
20.5 
34 
18 
all excl. 
ca. 21 
> (?) 
5 *-s 
23 
14 
10.5 
5-5 
II 
21 
33 
*9 
all excl. 
? 
» 
39 
16.5 
9-5 
8 
4 
9 
d -5 
31 
16 
all excl. 
20 
» (?) 
31 
15 
9-5 
7 -* 
4 
7 
1 1 
26 
'4 
all excl. 
17 
Falkland ( 
Islands / 
31 
d -5 
10.5 
7 
3-5 
6.5 
12 
28 
16 
all excl. 
? 
St. 22 
29 
h 
9-5 
6. 5 
4 
7 
h 
31 
16 
I in contact 
f 
» 59 
1 1 
6 
5 
3-5 
2 
3 
4 
17—18 
11 
all excl. 
5 
* Probably a hybrid between St. Agassizii and St. Neumayeri. 
