‘s RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 173 



The following are the results, arrived at by de Man (1895), as to 
the shape of the carapace: 
1°. In both sexes the proportion of the distance between the external 
orbital angles and the length of the carapace is the same. 
2°, In the © the posterior margin is about half the length of the cara- 
pace, and always considerably shorter than the breadth of the front; 
in the 9, on the contrary, the posterior margin is much more than 
half the length of the carapace and broader or only very slightly 
shorter than the breadth of the front. 
The distance between the epibranchial teeth is proportionally much 
greater in the Q than in the o’, so that in the latter sex the cara- 
pace appears to be narrower, in proportion to its length. From this 
we conclude, that in the 9 the carapace is much more strongly nar- 
rowed anteriorly than in the ¢''). De Man supposes this character 
to be a sexual difference, though, with regard to the few specimens 
examined, it cannot be said with certainty. 
Now, if we put together some records in literature about the dimen- 
sions of the species, and these are arranged for each sex separately, the 
following table is arrived at: 
Ore 

2 ; 3 4 B) iea'G 7 8 
Ss S S of eee 2 ¢ 
between ext. orb. angles . | 
(100) 38.33(100) 32.—(100) 29.—(100) 28.—(100) | 32.(100) 29.—(100) 28—(100) 27.75 (100) 
between epibranch. teeth ? | 
(100) 43.— (112.2) 34.5 (107.8) 31.25 (107.8) 30.5 (108.9) | 35.— (109.4) 33.— (113.8) 30.— (107.1) 31.75 (114.4) 
h of carapace 
(90.4) 36.5 (95.2) 28.5 (89.0) 26.— (89.6) 25.5 (91.0) | 80.— (93.4) 26.25 (90.5) 25.— (89.8) 25.66 (92.5) 
rior margin of carapace | 
(42.2) 17.5 (45.6) 14.5 (45.3) 18—(44.8) 14— (50.0) | 16.—(50.0) 16.— (55.2) 14.— (50.0) 14.5 (52.3) 
lth of front 
(50.6) 21.5 (56.0) 17.75 (55.5) 16.25 (56.0) 16.-—(57.1) | 18.5 (57.8) 15.5 (53.4) 16.— (57.1) 15.— (54.0) 
y N°. 1 is the large o of the Museum from Java, n°. 2 and 3 spe- 
cimens of de Man (1887), n”. 4: 
n°, 7: de Man (1895), n°. 8: Lenz, n°. 9 de Man (1895). 
de Man (1895), n°. 5 and 6: Lenz, 
For the sake of better comparison we take the distance between ex- 
ternal orbital angles 
— 100, and, parting from this, we arrive at the 
numbers, entered in brackets. It may, then, be concluded: that indeed 
the proportion of the distance between the external orbital angles and 
the length of carapace is nearly constant in both sexes and at different 

1) Lenz says, that, according to de Man, the length of the carapace with advancing age 
increases in proportion to its breadth, but I have not succeeded in finding out, where this pre- 
sumption has been written by de Man, 
