399 



4th pair less deep than the preceding pair. Urosome comparatively large and 

 massive, with the segments produced dorsally. Eyes distinct and scarcely coales- 

 cent; below them on each side, a minute accessory eye. Antennae compara- 

 tively slender, the superior one shorter than the inferior, and having the 

 accessory appendage rather fully developed. Oral parts normal : Anterior lip 

 rounded, with a compressed median projection; posterior lip with the inner 

 lobes well developed. Mandibles rather strong, but of quite normal structure, 

 the cutting part being distinctly dentated, and the molar expansion well 

 defined, palp comparatively small. First pair of maxillse with the basal lobe 

 rounded, and edged with numerous ciliated setae ; 2nd pair with the outer lobe 

 narrower than the inner. Maxillipeds nearly as in Syrrhoe. G-nathopoda com- 

 paratively much prolonged and densely setous, carpus greatly elongated and 

 very narrow, propodos simple linear, not subcheliform. Pereiopoda short and 

 stout, the 3 posterior pairs successively increasing in size, and having the basal 

 joint greatly expanded. The 2 anterior pairs of uropoda normal; last pair 

 rather large, with the rami lanceolate, the outer one with a small terminal 

 joint. Telson very narrow and elongated, deeply cleft. 



Ixemarlcs. — The present genus was established by Prof. Lilljeborg 

 in the year 1865, to include the species described in the sequel. With this, 

 tlie genus Tessarop.t of Norman is iindoubtedly identical. Among the charac- 

 teristics distinguishing the present genus from the other SyrrJioidoe, may be 

 named the very full development of the accessory appendage of the superior 

 antennae, the rather diiferent structure of the gnathopoda, and the presence 

 of an accessory eye on each side, below the true eyes, which are not 

 completely coalesced as in Syrrlwi-. The genus comprises as yet but a 

 single species, to be described in the sequel. 



5. Tiron acanthurus, Lilljeborg. 



(PI. 140). 



Tiron acanthurus, Lilljeborg, On the Lysianassa magellanica etc. p. 16. 



Syn. : Syrrhoe bicuspis, Goes. 

 » Tessarops hastatus, Norman. 



Body moderately slender and somewhat compressed, with the back 

 evenly rounded, and the posterior edge of the segments of metasome serrated 

 in the dorsal part. Segments of urosome each produced dorsally to a coni- 

 cally pointed, deflexed projection, the posterior of which is somewhat smaller 

 than the 2 anterior. Cephalon about the length of the first 3 segments of 

 mesosome combined, and produced in front to a comparatively short deflexed 



