THE GENEALOGY OF THE CRAYFISHES. 
SUccESSIVE FORMS OF THE ASTACOMORPHOUS TYPE, 
- Recent 
Potamobiide. Homarina. 
345 
. Later Tertiary 
Astacus 
(Idaho), 
Ik 
Earlier Tertiary. 
Hoploparia. 
Iv. 
Cretaceous. 
Asta 
ius, Pseudastacus, Enoploclytia, Hoploparia. 
. Wealden 
(Fresh Water). 
. Jurassic, 
Pseudastacus Eryma. 
. Liassio. 
VIII. 
Triassic. 
x 
Permian. 
Carboniferous. 
Anthrapaleemon 
xi. 
Devonian. 
XI. 
Silurian. 
xXIIL. 
Cambrian. 
If an Astacomorphous crustacean, having characters 
intermediate between those of Hryma and those of 
Pseudastacus, existed in the Triassic epoch or earlier ; 
if it gradually diverged into Pseudastacine and Erymoid 
forms; if these again took on Astacine and Homarine 
