ASTACUS. ain 
eyes. The areola is broad, about one half as broad as long. The telson is 
notched on each side, and furnished with one or two spines, but it is not 
divided by a transverse suture. In this respect these species resemble the 
Parastacinee of the Southern hemisphere. The transverse suture of the tel- 
son is most complete in the genus Cambarus and in the European Astaci. 
The Astaci of Western North America occupy a middle ground in this 
regard, the suture being incomplete or absent. 
In all the male specimens of Cambaroides that I have seen (one A. Dauii- 
cus, three A. Japonicus), the first abdominal appendages are divided into two 
sections by a transverse suture. The distal portion of these appendages is 
so closely rolled and consolidated that a mere groove remains on the inner 
side. The tip is truncate, and furnished with a few short blunt teeth or 
tubercles. I suspect the existence of two forms of the male here, as in Cam- 
barus, for in the male specimen of A. Dawicus the hooks on the thoracic legs 
are strongly developed, and some of the teeth at the end of the first abdomi- 
nal appendages are brown and horny at the tips, whilst in the three male 
A. Japonicus the hooks of the thoracic legs are weak, and the terminal teeth 
of the first abdominal appendages are smaller and not of a horny texture. 
The second pair of abdominal appendages of the male are somewhat dif- 
ferent from those in the genera Cambarus and Astacus proper. The terminal 
part of the endopodite, which retains the membranous character of the ex- 
opodite in Cambarus and Astacus proper, is here corneous, very short, and 
closely applied to the rolled lamella which lies on the inner side of the 
appendage. The rolled part assumes a somewhat triangular sbape, as in 
Cambarus and the Astaci of Western North America.* 
In the female of A. Schrenckit there is a transverse tubercle behind the 
sternum of the penultimate thoracic somite, much as in Astacus proper. In 
A, Dauricus and A. Japonicus this transverse tubercle or ridge is hollowed out 
behind, but still remains closely soldered to the sternum. The first abdomi- 
nal somite of the female is devoid of appendages, as in the’ American species 
of Astacus and in the Parastacine, 
In the number and arrangement of the gills, Cambaroides agrees with 
Astacus, and differs from Cambarus. 
The post-orbital ridge is slightly developed in all the species. It is least 
prominent in A. Japonicus, in which even the anterior end of the ridge is 
* The reader is referred to page 17 of Hagen’s Monograph, and to page 146 of Husley’s “ Crayfish,” for 
a general description of these appendages in Cambarus and Astacus proper. 
