342 DISTRIBUTION AND XTIOLOGY OF THE CRAYFISHES. 
and left their remains in the mud of the ancient sea 
bottom. 
Eryma is the only crustacean, which can be certainly 
ascribed to the Astacomorpha, that has hitherto been 
found in the strata from the Middle Lias to the litho- 
graphic slates; which last lie in the upper part of the 
Jurassic series. In the freshwater beds of the Wealden, 
no Astacomorpha are known, and although no very great 
Fig. 81.— Hoploparia longimana (% nat. size).— ep, carapace ; 
7, rostrum, T, telson; XvV., XVI., first and second abdominal somites ; 
10, forceps ; 20, last abdominal appendage. 
weight is to be attached to a negative fact of this kind, it 
is, so far, evidence that the Astacomorpha had not yet 
taken to freshwater life. In the marine deposits of the 
Cretaceous epoch, however, astacomorphous forms, which 
