ASTACUS. 127 



eyes. The areola is broad, aljout one half as broad as long. The tt'Ison is 

 notched on each side, and fnrnished 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. Daun- 

 CHS, three A. Jcqwnictis), 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. Danricus 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. Japonkus 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- 

 opodita 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 ^. SchrencJcii there is a transverse tubercle behind tiie 

 sternum of the penultimate thoracic somite, much as in Astacus proper. In 

 A. Daiuiciis and A. Jajjomcus this transverse tubercle or ridge is holloAved 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 Parastacintfi. 



In the number and arransrement of the Q-iUs, Cambaroides acrrees 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 



* Tlie reader is referred to page 17 of Hagcu's Monograph, and to page 116 of Huxley's "Crajfisli," for 

 a general description of these appendages in Cambarus and Astacus proper. 



