50 
1838. Hymenosoma (sub-gen. Leachium), McLeay, in Smith’s 
Illustr. Zool. S. Africa, p. 68. 
1843. Hymenosoma, Krauss, Siidafrik. Crust., p. 51. 
1886. Hymenosoma, Miers, Challenger Brachyura, Reports, 
Vol, XVII, p. 279: 
The genus has been commonly assigned to Leach, but neither 
Desmarest nor any of his successors has given a reference to 
the place of publication. Leach probably only gave the name 
in manuscript. It is appropriate to the membranaceous 
character of the integument. Alcock distinguishes three 
types in the family, in one of which, exemplified by Hymeno- 
soma, “there is no epistome and the external maxillipeds 
almost encroach on the bases of the antennules, which appen- 
dages are not connected by the front.’ Miers says, “‘ Scarcely 
any trace exists of an epistome.” Of the third maxillipeds 
Miers says that they are not arcuated, and have the third and 
fourth joints well developed, the fourth usually obliquely 
truncated, and bearing the following joint near its antero- 
external angle, at the distal extremity. The pleon of the 
male, he states, is very narrow, six-jointed, its base rarely 
occupying the whole width of the sternum between the last 
ambulatory legs. 
Targioni Tozzetti, in Crost. Brachiuri of the Magenta, 
pp. 179, 184, speaks of the pleon in the male of H. laeve as 
seven-jointed, but that is perhaps an error. Latreille affirms 
that in this genus the number of the pleon segments varies, 
but never exceeds six. Tozzetti supposed that only males 
were known, probably being unaware that Krauss refers to 
the females of H. orbiculare as being smoother and much 
smaller than the males. ; 
Hymenosoma geometricum, Stimpson. 
1858. Hymenosoma geometricum, Stimpson, Pr. Ac. Philad., 
p. 108 (54). 
1877. Hymenosoma geometricum, Targioni Tozzetti, Crost. 
Brachiuri Magenta, p. 182. 
1886. Hymenosoma orbiculare, var (?) geometricum, Miers, Chal- 
lenger Brachyura, Reports, Vol. XVII., p. 280. 
Stimpson, who obtained both species together in Simon’s 
Bay, says that his H. geometricum is tolerably near to H. 
orbiculare, but with the third joint of the third maxillipeds 
much more slender, scarcely shorter than the fourth joint ; 
the hepatic region armed behind the angle of the orbit with a 
