666 



ARTHROPODA 



SUB-KINGDOM VII 



being just behind the excurrent gill opening. Palaeocorystes, 'Bell (Fig. 1397), ranges 

 from the Gault to Eocene. Eucorystes and Necrocarcinus, Bell (Fig. 1398), are Cre- 

 taceous ; Hepatiscus, 

 Bittner, is Eocene ; 

 Calappa and Ma- 

 tuta, Fabr., range 

 from Eocene to 

 Recent. 



(4) In the 

 Oxyrhyncha, or tri- 

 angular crabs, the 



FIG. 1398. 



FIG. 1397. 



Palaeocorystes Stokesi, 

 Mant. sp. Upper 

 Greensand; Cam- 

 bridge, England. 



w 



FIG. 1399. 



Necrocarcinus tricarinatus, 

 Bell. Greensand ; Cam- 

 bridge, England (after Bell). 



Micromaia tuberculata, 

 Bittner. Eocene ; San 

 Giovanni Illariene, Italy 

 (after Bittner). 



cephalothorax is 

 broad behind, 

 pointed in front, 

 and the external 

 Fossil forms few and small. 



maxillipeds (buccal frame) are quadrilateral in outline. 



Micromaia, Bittner (Fig. 1399), and 



Microthorax, Noetling, are Eocene and 



Miocene respectively. Lambrus, Leach, 



is Eocene and Recent. 



(5) The Cyclometopa (Cancroidea) 



have a broad carapace, arcuate in front 



and narrowed behind, without prominent 



rostrum. The tribe is subdivided into 



the swimming crabs (Portunidae) and 



shore crabs (Cancridae), the former being 



distinguished by their lamellate feet, the 



fifth pair terminating in a broad flattened 



paddle. To the first group belong Nep- 



tunus and Achelous, de Haan ; Charybdis, 



Dana ; Portunites, Bell ; Psammocarcinus, 



M.-Edw. (Fig. 1400), etc., which make 



their appearance in the Eocene. The 



Cancridae are older ; Palaeocarpilius, M.- 

 Edw., appearing in the Upper Cretaceous and Eocene; and Panopaeus, M.-Edw., 



ranging from Cretaceous to 

 Recent. Harpactocarcinus, 

 M. - Edw. ; Lobocarcinus, 

 Reuss (Fig. 1401) ; Xan- 

 thopsis, M'Coy (Figs. 1402, 

 1403), are very abundant 

 in the Eocene ; Atergatis, 

 de Haan, in the Oligocene ; 

 Xantho and Cancer, Leach, 

 in the Neocene. Neptocar- 

 cinus and Carcinocarcinus, 

 Lorenthey, are described' 

 from the Eocene of Hungary 

 and Bavaria respectively. 

 (6) The Catometopa have 



FIG. 1400. 



Psammocarcinus Hericarti, Desm. sp. Middle Meeres- 

 sand (Miocene); Le Gue-a-Tresnies, France (after A. 

 Milne-Edwards). 



Lobocarcinus Paulinc-Wiirtcmbergicus, v. Meyer. 

 near Cairo, Egypt. Male. 



FIG. 1401. 



Eocene ; Mokkatam, 



the carapace quadrilateral 

 in outline, the front being abruptly truncated or slightly arcuate, and the sides nearly 

 straight and converging behind. Living species are marine, fluviatile, or terrestrial. 

 Galenopsis, Coeloma, M.-Edw. (Fig. 1404); Litoricola, Woodw. ; and Palaeograpsus, 



