REPORT ON THE BRACHYURA. 
215 
instead of presenting an obscure median and two lateral sinuses is divided into two lobes 
by a deep, triangular median notch (see the figure). I have never observed such a varia- 
tion to anything like the same degree in any other species of the genus. 1 
These specimens have the following dimensions : — 
Adult $ . 
Lines. 
Millims. 
Length of carapace, nearly . 
13 
27 
Breadth of carapace, nearly . 
161 
34-5 
Adult $ . 
Length of carapace, nearly . 
14 
29 
Breadth of carapace, 
m 
38 
Thelphusa ( Potamonautes ) perlatci, Milne Edwards. 
Thelphusa perlata , Milne Edwards, Hist. Nat. Crust., vol. ii. p. 13, 1837 ; Ann. d. Sci. Nat., 
ser. 3, Zool. xx. p. 209, 1853. 
„ „ A. Milne Edwards, Nouv. Archiv. Mus. Hist. Nat., vol. v. p. 179, pi. ix. 
fig. 3, 1869. 
„ ,, MacLeay, Annulosain Smith, Zool. of South Africa, p. 64, 1849, Potamonautes 
in text. 
South Africa, Wellington and Cape Town (in the rivers). A good series is in the 
collection. 
The largest male has the following dimensions : — 
Adult $ . 
Lines. 
Millims. 
Length of carapace, 
22 
46-5 
Breadth of carapace, 
30J 
64-5 
Length of large chelipede, . 
47J 
100-5 
The postfrontal crest is distinct and continuous in the smallest specimen in the series, 
a male, whose carapace is not 4 lines (8 ‘5 mm.) in length, and 5 lines (10 mm.) in width. 
Thelphusa ( Geothelphusa ) dehaanii, White. 
Cancer ( Thelpliusa ) berardii, de Haan, Crust, in v. Siebold, Fauna Japonica, p. 52, pi. vi. fig. 2, 
1835. 
Thelphusa dehaanii , White, List Crust. Brit. Mus., p. 30, 1847. 
,, „ Milne Edwards, Ann. d. Sci. Nat., ser. 3, Zool. xx. p. 212, 1853. 
„ „ A. Milne Edwards, Nouv. Archiv. Mus. Hist. Nat., vol. v. p. 174, 1869, 
and references to synonyma. 
Japan, in paddy fields near Lake Biwa, May 1875 (a male) ; at Hakona, at an eleva- 
tion of 2,500 feet above the sea-level, May 1875 (two small males) ; near Kobe, June 
1875 (three males). 
1 An obscure median excavation of the front is, however, occasionally seen, as for instance in an adult male 
Thelphusa africana, A. Milne Edwards, in the collection of the British (Natural History) Museum. 
