208 A HISTORY OF RECENT CRUSTACEA 
posterior face of which there is a pit or depression, an 
arrangement designated by Dr. Hagen as the annulus 
ventralis. Mr. Faxon enumerates no less than fifty-five 
species, twenty-one of them being described by him as new 
in 1884. Cambarus Diogenes, Girard, which is_ widely 
distributed in the United States, constructs curious 
‘chimneys’ at the mouth of its burrows, and Cambarus 
dubius, Faxon, it is said, ‘makes mud chimneys like C. 
Diogenes, which it seems to represent in the mcuntain 
regions, O. Diogenes belonging to the low lands.’ Cam- 
barus argillicéla, Faxon, is closely related to the two pre- 
ceding species. The types of it were dug out of burrows 
in solid blue clay in Detroit, Michigan. ‘The burrows 
were three to five feet deep. At the bottom of each 
burrow was a pocket in a layer of loose gravel and clay, 
holding water. Just above the water-line an enlargement 
in the burrow formed a shelf on which the animal rested.’ 
It is a pleasing picture of retirement, safety, and comfort, 
if one can accommodate one’s mind to the feelings and re- 
quirements of a crayfish. Cambarus pellucidus (Tellkampf) 
is the blind species of Mammoth Cave, Kentucky, in which 
it is noticed as a singular circumstance that Cambarus 
Bartonii (Fabricius) occurs with well-developed eyes. 
Cambaroides, Faxon, 1884, is only introduced by its 
author as a sub-genus of Potamobia, but it may as well 
follow its destiny at once and become a genus. Huxleyin 
‘The Crayfish’ mentions Astucus dauricus, Pallas, and 
Astacus Schrenkii, Kessler, as restricted to the basin of the 
Amur, which sheds its water into the Pacific over against 
Japan. He points out that the branchial system of the 
Amurland Astaci is apparently the same as that of the rest 
of the genus, but that the second and third trunk-legs in 
the male have a hook-like process on the third joint, and 
that the females have the transverse prominence already 
noticed in Cambarus. It is on this combination of charac- 
ters from Cambarus and Potamobia that Faxon has founded 
his Cambaroides, to include the two species just mentioned 
and the Astacus japonicus of de Haan. In this species he 
suspects the existence of two forms of the male, a pecu- 
