LYSIANASSIDAE 



57 



Remarks. Antero-lateral angle of head rounded (but not so blunt as in Chevreux's 

 figure) in the young, becoming subacute in the <$ and half-grown specimens, and acute 

 in the large $. A medio-dorsal keel from peraeon segment 4 to pleon segment 4, 

 stronger posteriorly, and more prominent in adult than young specimens. If the pleon 

 be flexed a basal depression is visible on segments 2-4. The 6th pleon segment bears two 

 dorso-lateral low keels which project as triangular lobes on either side of the base of the 

 telson (cf. Liljeborg, he. cit., quoted under Eurythenes, infra, p. 7). 



Antero-inferior angle of pleon segment 1 in young rounded, in adult quadrate; 

 postero-inf erior angle of segment 2 with a small point ; inferior margin of pleon segment 3 

 convex in young, nearly straight in adult $. The antero-inferior angle and margin is 

 feebly costate, and on segments 1 and 2 there is a feeble oblique keel. 



The epistome is considerably more prominent than described by Chevreux, and in 

 fact does not differ essentially from that of Eurythenes gryllus (Sars, 1895, pi. xxx). 



Fig. 21. Katius obesus, Chevr. a. Pleurae of pleon segments 1-3, adult ? (St. 101). b. The same, juvenile 

 (St. 78). c. Spine from apex of outer lobe of maxilla 1. d. Apex of outer plate of maxilliped. e. Anterior 

 margin of head with basal joints of antenna 2, epistome and upper lip. 



Basal joint of antenna 2 large, bulbous, visible externally (as in Eurythenes). Maxilla 1, 

 outer lobe with spines which bear acute and rather widely spaced denticles (as in 

 Eurythenes), inner lobe with 2-4 plumose setae in young, five in adult. Maxilliped, 

 outer plate with minute wart-like spinules on inner margin (as described by Schellen- 

 berg for Eurythenes, 1927, p. 678), 2-3 more obviously spiniform ones distally, and 2-3 

 plumose setae on outer distal margin. 



Branchiae with moderate folds, seemingly indicated in Chevreux's fig. 3 C, but not 

 mentioned in his text. Arising from near the base of each branchia on segments 2-7 

 posteriorly and externally is a small irregularly triangular accessory lobe. 



After the above remarks there would seem to be no need to harp further on the 

 similarity of Katius to Eurythenes. Besides the dactyli of peraeopods 1-5 and the side- 

 plates, a further difference may exist in the branchiae, but Liljeborg 's statement (loc. 

 cit. under Eurythenes, p. 6) ought to be confirmed. 



