CLASSIFICATION OF THE MAIOID CllUSTACEA. 669 



* Mesorhoea, Stimpson. E-esembles Solenolambrus in the 

 carapace, legs, pterygostoraian and hepatic cliaiinels ; but the 

 efferent branchial channels meet in the middle of the endostome 

 or buccal cavity, which has a triangular projection and a deep 

 notch in its vertical laminiform wall. The third joint of the 

 outer maxillipedes is produced forward at its internal angle and 

 conceals the palpus. Type Mesorhoea sexsjjinosa, Stimpson. 



This remarkable genus indicates an approach on the part of the 

 Maioidea to the Oxystomatous crabs, as has already been stated. 



§§ Carapace more or less laterally expanded. 



Ceyptopodia, Milne-Udwards. Carapace transversely tri- 

 angular, with the lateral margins greatly produced, and conceal- 

 ing the ambulatory legs, the posterior margin also prolonged 

 backward. Eront very prominent. No ridges on the ptery- 

 gostomian regions. Type Cryptopodia fornicata (Fahv.). 



Heteeocetpta, Stimpson. Carapace as in Cryptopodia, but 

 without the posterior expansion. A strougiy-marked ridge on 

 the pterygostomian region, defining the afferent channel. Type 

 Heterocrypta granulata (Gibbes). 



CEthea, Zeffc^. (Plate XIII. fig. 10.) Cara^pace transversely 

 cval or elliptical, with the lateral margins produced as in Crypto- 

 podia, and dentated. JN^o posterior expansion. K"o ridge on the 

 pterygostomian region. Type CEthra scruposa (Linn.). 



This genus, although somewhat resembling Cancer and Efisus 

 in external form, is much more nearly allied to Cryptopodia in 

 the characters of the cephalothorax and antennae, and must be 

 arranged with that genus, as has been done by Stimpson and 

 S. I. Smith. 



(The genus 'Eurynolam'brus, which is placed by MM. Milne- 

 Edwards and Lucas and by Dana with the Parthenopidss, and 

 which in the triangular and expanded carapace has certainly 

 much resemblance to Cryptopodia, has really far more affinity 

 with Cancer in the form of the orbital and antennal region. The 

 basal joint of the antennge, as in that genus, is much enlarged, 

 and excludes the flagellum from the orbital hiatus. The front is 

 bilobate ; and the anterior legs have not the trigonous form charac- 

 teristic of Cryptopodia and its allies. The lateral expansions of 

 the carapace are far smaller, and do not conceal the ambulatory 



