ZOOLOGISCHE MEDEDEELINGEN — DEEL Ill. 




From the rather long list of records we should infer, that this species 
is generally distributed all along the Indo-Pacific coasts. De Man, however, 
in 1902 (Abhandl. Senckenb. Gesellsch., Bd. 25 Heft 3 p. 588—541) 
first called attention to the fact that the original specimen of Japan 
differs somewhat from Indian specimens, originating from Amboina and 
Ternate, not only in the lateral margin of the outer orbital angle being 
rather strongly convex in the Japanese or typical form and straight or 
nearly so in the Indian specimens, but especially in the penultimate 
segment of the male abdomen being more than twice as broad (at the 
posterior margin) as long in the specimen of de Haan, but exactly twice 
as broad as long, or slightly less, in the latter specimens from Amboina 
and Ternate, which induced him to establish a subspecies zndica for these 
Indian specimens. I have thought it necessary to examine all the spe- 
cimens of our Museum again and found that those from East-India did 
indeed agree with de Man’s subspecies; whereas in Japanese specimens 
the posterior margin of the penultimate segment of the male abdomen 
was always more than twice the length of this segment, this proportion 
proved to be less in Indian specimens. Besides it seemed to me, that the 
epibranchial tooth behind the external orbital angle is more strongly 
curved upward in the Japanese form than in the subspecies indica. Ac- 
cording to this result I have strong reason to believe that the typical 
bidens oceurs in Japan and in neighbouring countries, but that at least 
the Indian specimens belong to the subspecies indica. Whether perhaps 
specimens from East Africa and from Australia must be referred to the 
same or to one or two other subspecies cannot as yet be decided. I have 
examined 4 <j of de Haan from Japan (3 of them were preserved dry) 
and give here the dimensions of the largest © (n°. 1), together with 
those of the type-specimen (n°. 2), measured by de Man (1.¢., 1902, p. 541). 
1 2 
Distance between external orbital angles 30.5 24.5 mm. 
- ‘ epibranchial teeth 30.— 24.—  , 
Length of carapace in the median line 25.— 20.25 , 
Posterior margin) of penultimate segment 8.25 (Ce 
Length of abdomen 4,— Bao iy 
It may also be possible, that among all the specimens recorded in 
the literature Ses. livida likewise is represented, for the outer aspect of 
this species is exceedingly like that of Ses. bidens, as de Man (I. c.) 
already remarked, and the two species may be only distinguished by 
1) Approximately. 
