’s RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 163 
under the head of this species). I have here maintained it as a distinct 
form on account of the following features: 
1°. The lateral margins of the carapace are slightly concave in the middle 
and subparallel in the Japanese typical specimen, distinctly diverging 
distally in Ses. impressa. 
2°. The carapace is yous smooth in the former, rough in the latter 
species. 
3°. The median sinus of the front is narrow and deep in Ses. impressa, 
shallow and broad in Ses. intermedia. 
4°. The outer surface of the palm of the chelipeds is nearly smooth in 
the Japanese species, with a distinctly defined group of large granules 
in the inferior part, but wholly covered with large, rounded tubercles 
in Ses. impressa. 
5°. The anterior margin of the carpopodite i is spined and the inner angle 
produced in Ses. impressa, but in Ses. intermedia the anterior margin 
is entire and the inner angle obtuse. 
6°. The meropodites of the walking legs are aoe hat more slender in 
the Japanese species and the carpo- and propodite are beset with long 
hairs, which hairs are nearly wholly absent in Ses. impressa. 
7°. The distance between the external orbital angles is about equal to 
the length of the carapace in the median line in Ses. impressa, but in 
the typical specimen of Ses. intermedia the latter is distinctly shorter 
(distance between external orbital angles 23 mm., between epibranchial 
teeth 24 mm., length of carapace in the median line 22 mm. '). 
It are especially the first, fourth and fifth points of difference, that 
seem to me to be of systematic importance, but before more material of 
Ses. intermedia is available, in order to acquire a look over the range of 
variation, the right of existence of the species remains doubtful, though, 
as de Man (1902, p. 530) rightly remarks, in the case of identity, the 
name of de Haan would have priority. 
55. Sesarma (Sesarma s.s.) jacobsoni Ihle. 
1912. Sesarma jacobsoni Ihle. Notes Leyden Museum, v. 34 p. 178, pl. 
9 — subterranean rivers on south coast of Java. 
Specimens in the Museum: 
5 o', 5 © (types of Ihle), Jacobson coll. 1911. 
1) De Man (1892, p. 387) says, that in Ses. intermedia the distance between the epibran- 
chial teeth exceeds that between the external orbital angles, but afterwards (1902, p- 528) he 
recognized, that the same may occur in Ses. impressa. He also remarks (1892, p. 337) that the 
hind margin of the type specimen of de Haan is damaged, but it is nevertheless possible to 
measure the length of the carapace. 
