THE GRAPSIDE 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, [yoplax, Hemiplax, Canp- 
toplax, Bathyplax, with many others. 
The genus Geryon, Kroéyer, 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- 
mitigated nuisance. 
Lamily 3.—Grapside. 
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 tne apex or the front outer angle of 
the fourth. The chelipeds in the aduit 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 
