THE GRAPSID^: 93 



A certain amount of uniformity, especially as regards 

 the flatness of the carapace, may be inferred to exist in 

 this family from the number of genera with names all alike 

 ending in -plax, as Acanthoplax, Hyoplax, Hemiplax, Ca-mp- 

 toplax, Bathyplax, with many others. 



The genus Gerj/on, Kroyer, 1837, may claim a passing 

 notice as one of those instances in which systematic 

 arrangement finds itself at fault. It is sometimes placed 

 among the Cyclometopa and sometimes among the Cato- 

 metopa. Mr. Miers says that it is very nearly allied to 

 Pseudorhombila and Pilumnoplax in the latter, and to 

 Galene in the former group. That, on the theory of the 

 evolution of different groups from a common stem, such 

 inosculant forms are almost sure to occur, has long been 

 recognised. Darwin himself humorously admits that while 

 as a theorist he delighted in coming across them, as a 

 naturalist engaged in classification he found them an un- 



o o 



mitigated nuisance. 



Family 3 . Graps idoe . 



i 



The carapace is depressed or moderately convex, more 

 or less quadrilateral, with the lateral margins straight or 

 slightly arcuate. The 'front' is never very narrow, in 

 general decidedly broad. The orbits and eye-stalks are 

 of moderate size. The third maxillipeds have the fifth 

 joint articulated at the apex or the front outer angle of 

 the fourth. The chelipeds in the adult male are usually 

 subequal, moderately developed. In the walking legs the 

 seventh joint is stiliform, compressed, and either smooth 

 or spiniferous. The pleon at the base usually covers the 

 whole width of the sternum between the last pair of legs. 



The species are almost always littoral or shallow-water 

 forms, with a rare exception in deep water. 



In this family there are about twenty-four genera 



Grapsus, Lamarck, 1801, is a wide-ranging genus 

 which was brought to the notice of Europeans a century 

 and a half ago in the species Grapsus maculatus (Catesby. 

 1743 and 1771), to which Bosc in 1802 applied the better 



