1904.] ASELLOTA-GROUP OF CRUSTACEANS. 303 



later years. In the following pages I describe six species examined 

 by myself of this type, five of which are considered new to science. 

 Having now such a rich material of an important and imperfectly 

 known genus at my disposal, I thought it appropriate to work it 

 out ; besides, I seize the opportunity of elucidating some points 

 of the morphology of the pleopoda in other Asellota, and discussing 

 the classification of the whole group, 



II. Descrijjtiou of the Gemos Stenetrium Hasio. 



Body oblong, three or four times as long as broad, rather 

 depressed, shaped nearly as in lanira. 



Head with the dorsal surface much broader than long ; in 

 advance of the anterior margin is seen a transverse area, the 

 frontal plate (PI. XIX. fig. 1 a, /), between the insertions 

 of the antennidee. When the head is stretched forward a large, 

 sloping, anteriorly rounded part is seen in advance of the frontal 

 plate ; this area is clypeus and labrum, and when the mandibidar 

 palps are in their natural position the distal part of their second 

 joint and the whole third joint are observed on the surface of the 

 clypeus. Eyes always distinct, but varying much as to shape, 

 size, and situation. 



Antennula? from somewhat shorter to a little longer than the 

 breadth of the head. Peduncle three- jointed ; basal joint oblong 

 but rathei' thick, longer and much thicker than any of the two 

 othei"S. Flagellum varies much in length and number of joints. 



Antennte nearly as long as or a little longer than the body, 

 very similar to those in lanira. The peduncle consists of foiir 

 short and two long joints : the first joint is always well developed 

 (and shows excellent specific characters) ; third joint on the outer 

 side with an exopod which is a subtriangiilar, oblong, setiferous 

 plate, with the lateral parts bent inwai-ds. 



Mouth-parts essentially as in lanira. Mandibles (PL XX. 

 fig. 3 a) moderately long ; lacinia mobilis of the left mandible 

 (fig. 3 h) consists of a thick, long, movable process and a few very 

 broad, long, a little curved setee, pectinate with exceedingly short 

 teeth along their anterior margin ; one of these setse proceeds 

 from the process itself near its base ; the articidating membrane 

 is broad on the lower side. Lacinia mobilis of the right mandible 

 (fig. 3 c) shows a number (in S. antillense about ten) of very thick 

 setae, nearly all with saw-teeth. Mandibular palp well developed, 

 three-jointed ; terminal joint rather broad and long, with 

 a comb of numerous fine setae. Hypopharynx (paragnatha) 

 (PL XX. fig. 3 d) rather deeply bifid ; each half has the 

 inner margin nearly straight and clothed with fine bristles 

 on its distal part ; the anterior angle rather rounded and 

 the outer margin very convex. — Maxillulae (fig. 3 e) slender ; the 

 inner lobe terminates in three curved, thick, plumose setse ; outer 

 lobe (fig. 3/) with a good number of very thick, curved spines, 

 coarsely serrate along at least one margin. Maxillae (fig. 3 g) 



