\st.\cus. 127 



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 

 Parastacinae 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. Dauri- 

 cm, three A. Japonicits), 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. Dauricus 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 homy 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 shape, as in 

 Cambarus and the Astaci of Western North America.* 



In the female of A Schrenckii 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 Parastac'nnr. 



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 



* Tlic reader i- referred to page 1 7 of Hagi n's Monograph, and to page 1 L6 'it' Huxley's " Craj fish," for 

 a genera] description of these appendages in Cambarus ami Amarus proper. 



