126 



S. OHTSUKA, G.A. BOXSHALL AND H.SJ. ROE 



with non-reduced outer seta (Fig. 11D). 



Maxillule (Fig. 12A): praecoxal arthrite with 5 bare spines 

 and 1 shorter process; coxal epipodite with 8 setae; coxal 

 endite with long, spinulose seta; vestigial basal seta present 

 (indicated by arrowhead); endopod bulbous, 1-segmented, 

 bearing 2 relatively long, spinulose setae terminally. 



Maxilla: first praecoxal endite with 2 setae and 1 vestigial 

 element, second with 2 spinulose setae; basal spine (Fig. 11F) 

 with 2 rows of spinules; setae on endopod well developed, 

 ornamented with row of long, simple spinules along inner 

 margin (Fig. 11G). Maxilliped (Fig. 12B): innermost seta on 

 fourth and fifth endopod segments (indicated by arrowhead) 

 not reduced; seta a on sixth endopod segment reduced; seta b 

 relatively long; setae c and d simply ornamented with spinules 

 along inner margin. 



Leg 1 with 2 outer spines on third exopod segment. Leg 4 

 with vestigial element on inner distal angle of coxa (Fig. 

 12C). Leg 5 (Fig. 12D-G): coxae and intercoxal sclerite 

 completely fused to form common base; coxa and basis 

 incompletely fused in right leg and separate in left. Right leg: 

 endopod (Fig. 12E) 1-segmented, spatulate, with minute 

 sensillum on outer proximal margin and tubular prominences 

 terminally; first exopod segment produced on outer angle, 

 with minute spine, second segment almost completely sepa- 

 rate from third, with 2 tufts of fine setules at inner distal 

 angle, minute sensillum at midlength of inner distal triangular 

 process (Fig. 12G) and outer terminal spiniform seta, third 

 segment triangular, tapering distally, with minute sensillum 

 at outer middle margin and short vestigial element termi- 

 nally; third segment with well developed muscles proximally. 

 Left leg: endopod (Fig. 12F) distinctly 2-segmented, first 

 segment produced terminally, second separate from first, 

 spatulate, covered by numerous fine setules on outer surface, 

 with attachment of muscles proximally; first exopod segment 

 similar to that of right leg, second expanded inwards with 

 outer seta subterminally, third segment small, separate from 

 second, with 2 elongate, chitinized processes terminally and 

 minute setule and scar of outer element proximally. 



Remarks. The fifth leg of the new genus exhibits a more 

 primitive state than Paraugaptilus in: (1) 2-segmented left 

 endopod; (2) both exopods 3-segmented. The right third exopo- 

 dal segment of Paraugaptiloides is certainly movable with well- 

 developed muscles originating in the preceding segment, while 

 the counterpart of Paraugaptilus is almost fused with the preced- 

 ing segment and has reduced musculature (see Figs 30F,32H). It 

 is probably not movable. In addition, the second segment of the 

 left endopod in Paraugaptiloides is likely to be movable as 

 indicated by the presence of a muscle extending between first 

 and second segments. 



Genus Arietellus Giesbrecht, 1892 



Diagnosis (emended). Female. Body relatively large, mea- 

 suring approximately 3 to 7 mm in total length. Prosome 

 pointed or rounded frontally; cephalosome separate from 

 first pedigerous somite; last prosomal somite with pair of 

 blunt dorsolateral processes and paired ventrolateral pro- 

 cesses, symmetrical or asymmetrical, strongly or weakly 

 produced backwards. Genital double-somite longer than 

 wide, with pair of gonopores ventrolaterally and copulatory 

 pore ventromedially; seminal receptacle relatively large, bul- 

 bous, located laterally. Anal somite large; anal operculum 

 not developed. Caudal rami symmetrical, longer than wide, 



divergent or not, with well developed setae II to VII. 



Antennule symmetrical, distinctly 20-segmented; posterior 

 margin fringed with long setules from segment I to X; 

 segments I to IV and XXIII to XXVIII fused; segments IV, 

 VI and XII without aesthetasc; compound segment 

 XXVI-XXVIII with 7 setae and aesthetasc. Antenna: first 

 endopod segment unarmed; second segment with 2 inner 

 setae, reduced in some species, and 5 setae and setule 

 terminally; exopod indistinctly 7- or 8-segmented, segment 

 VIII unarmed. Mandibular gnathobase lacking tuft of setules 

 at midlength; 3 cusped teeth on cutting edge, dorsalmost of 

 which bifid at tip. Mandibular palp: endopod absent; first 

 exopod segment with reduced or normal seta, outer seta on 

 fifth segment vestigial. Maxillule: praecoxal arthrite with 6 

 elements (5 spines and 1 process); coxal endite bearing 1 

 relatively short, thick seta, fringed with long setules; coxal 

 epipodite with 8 setae; outer basal seta absent; endopod 

 rudimentary, almost fused to basis or 1-segmented, bulbous, 

 with 1 seta terminally. Maxilla: first and second praecoxal 

 endites carrying 1 and 2 setae, respectively; basal spine with 2 

 rows of spinules; endopod setae armed with stout spinules 

 fringed with lamellar structure basally. Maxilliped: se^al 

 formula of endopod segments of maxilliped: 1,4,4,3 or 2,3 or 

 2,4 (innermost seta on fourth and fifth segments reduced or 

 completely lacking in some species); setae a and b on sixth 

 segment vestigial. 



First and third exopod segments of leg 1 bearing 1 and 2 

 outer spines respectively. Leg 5 reduced; coxae and inter- 

 coxal sclerite fused to form common transverse plate; basis 

 and coxa separate or fused; right basal seta longer than left; 

 endopod fused with basis, represented by small knob bearing 

 1 to 3 setae terminally, vestigial in some species; exopod 

 1-segmented, bulbous, carrying 1 terminal spine or almost 

 fused to basis, unarmed. 



Male. Body as in female, about 4 to 6 mm in total length. 



Left antennule 19-segmented, geniculate; segment XXI 

 fused with XXII; segments II and III with 1 seta; segment 

 XIII with seta; segments I to IX fringed with row of long 

 setules along posterior margin. 



Second endopod segment of antenna with 1 long and 1 

 short seta medially; first exopod segment of mandible with 

 normally developed seta. 



Leg 5: coxae and intercoxal sclerite fused to form common 

 plate; right coxa and basis incompletely fused; right basal seta 

 remarkably or normally elongate. Right leg: endopod 

 1-segmented, unarmed; exopod indistinctly 3-segmented, dis- 

 tal 2 segments incompletely fused, second segment with stout 

 process on inner angle, third segment spatulate, with 0-2 

 vestigial elements. Left leg: endopod indistinctly 2-segmented 

 or 1-segmented, unarmed; exopod 3-segmented, second seg- 

 ment expanded medially, third segment incompletely fused 

 with preceding one, bearing 2 terminal spines, with or 

 without outer minute spinule. 



Type species. Arietellus setosus Giesbrecht, 1892 (mono- 

 typic). 



Other species. A. aculeatus (T. Scott, 1894); A. giesbrechti 

 Sars, 1905; A. pavoninus Sars, 1905; A. plumifer Sars, 1905; 

 A. simplex Sars, 1905 (= A. major Esterly, 1906); A. armatus 

 Wolfenden, 1911; A. minor Wolfenden, 1911; A. pacificus 

 Esterly, 1913; A. tripartita C.B. Wilson, 1950; A. sp. Brad- 

 ford, 1974; A. mohri (Bjornberg, 1975), new combination; ,4. 

 sp. briefly described here. 



