REPORT ON THE BRACHYURA. 
37 
As Professor A. Milne Edwards lias shown, it is probable that the described species of 
this genus, eleven in number, are all to be regarded as synonymous with the type species, 
Mensethius monoceros (Latr.). 1 
This species is very widely distributed throughout the Oriental region, from the Red 
Sea and East African coast to the Fiji Islands, and has not, I believe, been recorded 
except from shallow water (depth not exceeding 1 8 fathoms). 
Mensethius monoceros (Latreille), var. angusta, Dana. 
Menxthius angustus, Dana, Amer. Journ. Sci. and Arts, ser. 2, vol. xi. p. 272, 1851 ; U.S. 
Explor. Exped., Crust., vol. xiii. p. 120, pi. iv. fig. 5, 1852. 
Three small male specimens, obtained off Nukalofa, Tongatabu, in 18 fathoms, 
lat. 20° 58' O'' S., long. 175° 9' 0" E. (Station 172), are referred to the variety 
designated by Dana, Mensethius angustus, of this very common and variable species ; 
they agree with his description and figure in the narrowness of the carapace and the 
slenderness of the elongated and slightly emarginate rostrum, although presenting some 
differences with regard to the number and arrangement of the tubercles of the carapace, 
e.g., the smaller tubercles of the gastric, cardiac, and branchial regions, which are much 
less distinct than in his figure. 
Another specimen, an adult male, obtained near Cape York, Australia, in 8 fathoms, 
lat. 10° 30' 0" S., long. 142° 18' 0" E. (Station 186), is of very different form, with 
a broad, very uneven, tuberculated carapace, flattened triangulate supraocular spines, 
and short rostrum, which scarcely exceeds in length the width of the carapace at the 
frontal region, and nearly resembles the variety figured by Dana [tom. cit., p. 122, 
pi. iv. fig. 7), as Mensethius subserratus, Adams and White. Danas specimens were 
from the Fiji and Samoan Islands. 
The dimensions of these specimens are as follows : — 
Adult $ , from Tongatabu (the largest). 
Length of carapace, rather over . 
Length of rostrum, nearly 
Breadth of carapace, nearly 
Length of a chelipede, about 
Length of first ambulatory leg, nearly . 
Adult $ , from Cape York. 
Length of carapace, nearly 
Length of rostrum, nearly 
Breadth of carapace, 
Length of a chelipede, about 
Length of first ambulatory leg, nearly 
Lines. Millims. 
3 7 
2 5 
3 5-5 
5 11 
6 12-5 
5 10 
2 4 
4 8-5 
5 11 
6$ 13-5 
1 Exception may, however, perhaps be made provisionally for Menxthius tuberculatus, Adams and White, from 
the Mauritius, in which the tubercles of the carapace are more developed than in any other variety known to me, and 
take the form of blunt spines on the branchial, cardiac and intestinal regions. 
