South African Crustacea. 79 



FAMILY TIKONICME. 



GEN. TIEON, Lilljeborg. 



1865. Tiron, Lilljeborg, N. Acta Soc. Upsal., Ser. 3, vol. vi., p. 19. 

 1906. Tiron, Stebbing, Das Tierreich, Amphipoda, pp. 275, 727. 



The three species which the genus now includes may be dis- 

 tinguished as follows : 



First three segments of pleon dorsally uni- 



dentate ; outer plate of maxillipeds with 



concave margin 1. T. thomsoni, A. 0. Walker. 



First three segments of pleon dorsally pluri- 



denticulate ; outer plate of maxillipeds 



with margin not concave 2. 

 Sixth joint of peraeopods extremely short ; 



telson armed with numerous spines . . . . 2. T. australis, n. sp. 

 Sixth joint of peraeopods not extremely short ; 



telson not armed with numerous spines . . 3. T. acanthurus, Lilljeborg. 



The new species has interesting peculiarities of the first maxilL^e, 

 and is further distinguished from T. acanthurus by a different shape 

 of the second joint in the fifth perseopods, but these features are less 

 easy to observe than those above given. 



TIRON AUSTRALIS, n. sp. 

 Plate XXXVIII. 



The general appearance closely agrees with that of T. acanthurus, 

 the head having a deflexed rostrum, the first three segments of the 

 pleon being postero-dorsally pluri-denticulate, and the fourth and fifth 

 each produced into a dorsal tooth, but here the tooth of the fourth 

 segment is much the shorter. The sixth segment has a scarcely 

 perceptible tooth, flanked on each side by two spines. The anterior 

 side-plates are finely crenate, the first and fourth smaller than the 

 second and third. 



The upper eyes are closely adjacent at the top of the head, each 

 composed of about ten cones, of which each lateral eye has only 

 four. 



The first antennae have the third joint shorter than the second, 

 and the second much shorter than the first. The flagellum is some- 

 what longer than the peduncle, 9-jointed in the female specimen, 

 7-jointed in the male, the first joint in the latter being distinguished 

 by its superior length and setose armature. The accessory flagellum 



