FISHERY BULLETIN: VOL. 85, NO. 2 



but clearly distinct on anterior part of fourth, sharp 

 and rather high more posteriorly, and produced in 

 short but strong spine on caudal margin of each 

 somite; sixth also bearing pair of minute postero- 

 ventral spines and 2 elongate cicatrices. Telson with 

 median sulcus weak, usually limited to anterior half, 

 flanked by paired longitudinal ridges reaching base 

 of second of 4 pairs of movable, marginal spines 

 situated at about 0.55, 0.75, 0.85, and 0.90 length 

 from basal margin. Mesial ramus of uropod surpass- 

 ing apex of telson by as much as 0.40 its own length; 

 lateral ramus overreaching mesial ramus by as much 

 as 0.33 its own length. 



Petasma of young individual lacking cincinnuli, 

 similar to juvenile petasma of P. gracilis. Petasma 

 of adults unknown. Curiously, only male available 

 21.5 mm CL with petasma still quite undeveloped. 



Appendices masculina and interna as in P. kath- 

 leenae. 



In small juvenile males, sternite XIV bearing 

 large, minutely setose prominence, semicircular in 

 outline; median plate of sternite XIII setose, elon- 

 gate (length 2-3 times basal width), and produced 

 in conspicuous apical spine. 



Thelycum (Fig. 18) with setose, moderately long 

 plate of sternite XIV broadly depressed and pro- 

 duced at either side in short anterolateral hood, 

 anteromedian margin varying from weakly convex 

 to concave or biconcave; fossa preceding plate rela- 

 tively short and bearing pair of small, oblique ridges. 

 Median plate of sternite XIII, also covered with 

 setae, relatively short (length 1.8-2.1 times basal 

 width), falling considerably short of anterior margin 

 of sternite XII; broadly lanceolate (maximum width 

 0.60-0.70 length), produced apically in acute spine, 

 and flat or slightly excavate; posterolateral margins 

 of plate, lacking bosses, abutting slender ridges ex- 

 tending posteromesially before curving laterally on 

 margin of sternite XIII. Sternite XII minutely 

 setose, strongly convex and crested by slender me- 

 dian carina ending anteriorly in sharp spine. 



Color, orange (Crosnier 1978). 



Maximum lengths.— Males, 22 mm CL (only juve- 

 niles known; the 33.5 mm CL cited by Crosnier 

 (1978) is a misprint, the specimen is a female); 

 females, 47.5 mm CL. 



Geographic and bathymetric ranges.— This species 

 has been found off Natal, South Africa, western 

 Madagascar, and in the waters of Indonesia to 

 southern Buru (Fig. 9). It occurs at depths between 

 834 and 1,200 m and was also taken in a trawl be- 

 tween 810 and 1,020 m. 



i?rn 



^^ Wf It^t^HH^fM-^--^ -^^f '" 



>^;s 



Figure 18.— Pseudaristetis sibogae (De Man), holotype 9 34 mm 

 CL, east Savu Sea, Indonesia. Thelycum. Scale = 2 mm. 



Discvssion.-The minutely setose pereopods and the 

 disposition of the deep groove lying dorsal to the 

 posterior part of the hepatic sulcus, which abuts the 

 cervical sulcus, distinguish P. sibogae from all the 

 species previously described. It also is distinctive in 

 having a longer optic calathus, the length of the 

 mesial margin being at least 1.45 times its distal 

 width instead of not more that 1.30. The tubercle 

 of the calathus in P. sibogae is almost always situ- 

 ated near its midlength, between the distal 0.4 and 

 0.6 length of the mesial margin rather than only as 

 far as 0.4 or more often less, except in the eye of 

 P. protenstis in which it is placed about at midlength. 

 In females of P. sibogae the median plate of ster- 

 nite XIII is shorter, its length 1.8-2.1 times the basal 

 width, than in females of its congeners, in which the 

 ratio is usually more than 2.1; in occasional speci- 

 mens of P. gracilis it is 2, overlapping the highest 

 ratios observed in P. sibogae. 



As stated above, the petasma of the adult of this 

 species is not known; however, the very large prom- 

 inence of sternite XIV, present in the 2 males ex- 

 amined, appears to be a diagnostic feature. These 

 specimens are 21 and 21.5 mm CL and, curiously, 



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