12 
THE VOYAGE OF H.M.S. CHALLENGER. 
bases of the eye-peduncles (but there are no distinct orbits). The merus of the exterior 
maxillipecles is sometimes distally rounded, the palms of the chelipedes are often some- 
what inflated. The ambulatory legs are slender and often very long. 
To the genera enumerated by me in 1879, as belonging to this group, the following 
are probably to be added : — 
Anisonotus, A. Milne Edwards. 
Anasimus, A. Milne Edwards. 
Apocremnus, A. Milne Edwards. 
Ergasticus, A. Milne Edwards. 
Lispognathus, A. Milne Edwards. 
Scyramathia, A Milne Edwards. 
Trachymaia, A. Milne Edwards. 
Gonatorhynchus , Has well. 
Platymaia, n. gen. 
Cyrotomaia, n. gen. 
Echinoplax, n. gen. 
Anisonotus apparently establishes the transition between Incichoicles in this group, 
and the Leptopodiinse. 1 
Platymaia , n. gen. 
Carapace depressed ; suborbiculate. Rostrum short, apparently tridentate, the 
median lobe arising from the distal end of the interantennulary septum. No praeocular 
but a supra and postocular spine. Epistoma very small, transverse. Post-abdomen (in 
the female) narrowest at base and broadening distally, thus obovate and subtruncated at 
the distal extremity, with all the segments distinct. Eyes short, with a distal tubercle, 
cornese somewhat dilated. Antennae with a short and slender basal peduncular joint, 
which does not reach the front ; the flagellum is well developed. Exterior maxillipedes 
with the ischium-joint rather broad, with a spine at the antero-internal angle ; the merus 
is slenderer than the ischium, articulating with the next joint at its antero-internal angle, 
which is not emarginate. Chelipedes (in the female) rather slender and short, spinuli- 
ferous ; spines of merus long. Ambulatory legs very considerably elongated ; those of 
the first pair having the fourth to last joints (merus to dactyl) armed with strong spines, 
which are longest on the anterior margin of the penultimate joints ; the second to last 
legs almost devoid of spines, with the penultimate joints dilated and compressed (as in 
Eurypodius) , and ciliated on the anterior margins ; dactyli elongated, slender and 
slightly arcuated. 
Platymaia is not very nearly allied to any genus of this family known to me. 
Its nearest affinities are perhaps with Euprognatha, Stimpson, 2 but it is at once distin- 
guished by the depressed and suborbiculate form of the carapace and the dilatation of the 
1 Professor S. I. Smith has recently proposed the designation Anamathia in place of Amathia, Roux, which name 
was previously used. Proc. U.S. Nat. Mus., vol. vii. p. 493, 1884. 
2 Bull. Mus. Comp. Zool., vol. ii. p. 122, 1870. 
