Classification of the Thalassinidea. 537 
have been used in the definitions below; but the evidence of 
each of these as to the relationships of the subgenera contra- 
dicts that of the rest, and there are none of those special 
features which are so useful in separating groups of species 
in other cases. Sooner or later, however, a considerable 
rearrangement is likely to be necessary. 
Subgenera: <Azius, Neaxius, Iconaxiopsis, Kiconaxius, 
Paraaius. 
Subgenus Axius, Leach, 1815. 
Definition: “Species of Agius with the flat area of the 
back and the cervical groove well marked, the eyes well 
pigmented, the antennal thorns both of a good size, pleuro- 
branchs on the second to fifth legs, vestiges of a podobranch 
and an arthrobranch on the second maxilliped, and a shallow- 
water habitat.” 
Species : 
Type. A. stirhynchus, Leach, 1815. Tr. Linn. Soc. xi. A. 
Subgenus NEAXIUS, n. 
Definition: “Species of Agius with the flat area of the 
back and the cervical groove well marked, the eyes well 
pigmented, the antennal thorns both of a good size, no 
pleurobranchs, vestiges of gills sometimes present on the 
second maxillipeds *, and a shallow-water habitat.’ 
Species : 
Type. A. acanthus, A. M.-Edw., 1879. Bull. Soc. Philom. [ =A, éalili- 
ensis (Borradaile), 1900]. I. 
A. plectorhynchus, Strahl, 1862. Mon.-Ber. Ak. Berlin, 1861. I. 
2 A. glyptocercus, Martens, 1869. __,, is a 1868. I. 
? A, Gundlachi (Martens), 1872. Arch. Naturges. xxxviii. i. HE. 
Subgenus Iconaxtopsis, Alc., 1901. 
Definition: “ Species of Azius with the flat area of the 
back and the cervical groove indistinct, the eyes almost or 
quite without pigment, the antennal thorns both of a good 
size, pleurobranchs on the second to fourth legs, vestigial 
gills on the second maxilliped, and a deep-water habitat.” 
Species : 
Type. A. laccudiwvensis, Alc., 1894. J. As. Soc. Bengal, Ixiii. I. 
A, andamanensis (Alc.), 1901. Ind. Deep-sea Macrura and Anomala, I. 
? A. farre (Ortm.), 1891. Zool. Jahrb. vi. Syst. i. 1. 
Subgenus Erconaxivs, Bate, 1888, 
Definition: “ Species of Awius with the flat area of the 
* A, plectorhynchus, specimens in Brit. Mus.; not A. acanthus, 
