118 MR. G. W. SMITH AND DR. E. H. J. SCHUSTER ON 



Since the .animals are never seen out of theii" burrows in the 

 day-time, very little is known as to their food or the means they 

 employ to obtain it, but it is probable that they are mainly 

 cai'nivoi'ous in diet, as the remains of earthworms, insect larvae, 

 .and probably land Crustacea have been found in their stomachs. 

 As has been pointed out elsewhere (' A Naturalist in Tasmania '), 

 the evergreen beech forests in Western Tasmania support a very 

 rich terrestrial fauna of land Amjjhipods (Talit7'us) which swarm 

 under the fallen beech leaves and timber, and numerous Myriopods 

 and insect larvse occur as well, affording abundant food in exactly 

 tlie situations which Engceus chooses for its burrows. 



The young are brought into the world and tended by the 

 female parent in the same way as in the ordinary crayfish, and I 

 have obtained females from their burrows with their young ones 

 •still attached to the swimmerets under the abdomen. At this 

 ^tage the young ones have all the characteristic features of the 

 adult, showing the same vaulted carapace and reduced abdomen. 



The interrelationships of the various species of Engceus may be 

 gathered from the key for the determination of the species given 

 on p. 119. 



The least modified and specialised species is E. mnictdarius from 

 Tasmania, Gippsland, and Victoria. This species has the general 

 form of the thorax and abdomen in a less aberrant condition than 

 the other species, and it is also more normal in its other characters, 

 possessing the last pleurobranch,theexopoditeon the third maxilli- 

 pede, and the two ilagella on the first antenna in a fully developed 

 condition. E. fidtoni from Victoria is closely related to this 

 species, but the exopodite of the third maxillipecle is rudimentary. 



The Tasmanian E. fossor and the Victorian species E. affinis, 

 victorievsis, and pliyllocercus are all closely related, and exhibit to 

 the full the peculiarly roof-shaped thorax and reduced abdomen ; 

 Avhile E. hemicirratidits is the most highly specialised, having lost 

 not only the exopodite of the third maxillipede but also the 

 posterior pleurobi'anch and the inner flagellum of the first 

 antenna. 



Genus Eng^us. 



Erichson, Archiv f, Naturg. vol. xii. p. 102 (1846); Huxlev, 

 P. Z. S. 1878, p. 769. 



The gill-formula is the same as in Astacopsis, Chceraps, and 

 Paracho'raps, except that the last pleurobranch may be entirely 

 absent. The posterior arthrobranchs are reduced in size. 



The ala of the podobranchs (PI. XIII. figs. 7 & 8 al.) is small 

 and inconspicuous as in Astacopsis, and it cariies a few filaments 

 with terminal hooks which are shaped as in Astacopsis. 



None of the other gill-filaments carry terminal hooks. 



The hooked setae on coxopodites and podobranchs are not 

 sharpl}' recurved, but resemble those of Astacopsis. 



The mandibles (PI. XV. figs. 16 & 17) have two prominent 



