THE GENEALOGY OF THE CRAYFISHES. 



3'45 



Successive Fobms of the Astacomobphous Type. 



L Recent Fotamohiidce. Homarina. Penteus, 



n. Later Tertiary fj^^ 



III. Earlier Tei-tiary. 



Hoploparia, 



IV. Cretaceous. Asiacus. Pseudastacus. Enoplodytia. Hoploparia. 



V. Wealden 



(Fresh Water). 



XIII. Cambrian. 



If an Astacomorphous crustacean, having characters 

 intermediate between those of Eryma 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 Homaiine 



