1006 A REVISION OF THE AUSTRALIAN ISOPODA, 



only about / th of an inch. The head is extremely large, more 

 than half the length of the pereion ; it presents in front a deep 

 mesial excavation, at the bottom of which is a tooth ; bounding 

 the excavation on either side is a tooth-like projection. The 

 pereion is as broad as the head in front, narrower behind ; the 

 hinder segments are slightly longer than the anterior. The pleon, 

 with the telson, is about equal in length to the last four segments 

 of the pereion ; its length is rather more than thrice its breadth. 

 The upper antennse are shorter than the lower, considerably 

 shorter than the head ; the three joints of the peduncle progres- 

 sively increase in length distally ; the flagellum, which is nearly 

 as long as the last joint of the peduncle, consists of a rudimentary 

 proximal, a longer second, and a very small terminal articulation, 

 the last ornamented with hairs. The inferior antennse are longer 

 than the superior, but shorter than the jaws ; their flagellum is 

 about the same length as the last segment of the peduncle, and 

 consists of seven articuli. The jaws are very large, longer than 

 the head ; internally, near the base, each presents a bifid tubercle ; 

 at the apex each is divided into three teeth, of which one is 

 rudimentary. The two anterior pairs of legs, which are a little 

 larger than the following pairs, have the ventral borders of the 

 merus and carpus each armed with two blunt spines ; in the 

 hinder pairs the place of these is taken by a series of very short 

 spinules. 



In the form of the jaws and their enormous size this species 

 differs from any others, as well as in the great relative size of the 

 head. Its nearest ally seems to be Anceus maxillaris, from which, 

 however, it is very far removed. 



I am indebted for the only specimen of this species I have seen 

 to Mr. Thos. Hewitt. It was found in Port Jackson. 



Fam. TanaiDjE. 

 Tanais tenuicornis. 

 [Plate L. Figs. 1—8.] 

 Paratanais tenuicornis, Haswell. Proc. Lin. Soc, N.S.W., 

 Vol. VI., p. 194, pi. IV. 



