FISHERY BULLETIN: VOL. 85, NO. 2 



mesially and with distal part, lying free but against 

 ventral surface of dorsolateral lobule, markedly con- 

 tracted just proximal to spatulate or paddlelike 

 terminal process. 



Petasma in juveniles lacking cincinnuli, specific 

 characters seemingly absent (Fig. 16C, D): dorso- 

 median and ventromedian lobules not completely 

 differentiated, but narrow, lapel-like flap present 

 along ventromesial margin; dorsolateral lobule 

 broad proximally, tapering gradually to rounded 

 mesial tip, and with distolateral margin gently 

 curved. Ventral costa arched throughout its length, 

 narrower and contracted distally. 



Appendixes masculina and interna as in P. 

 kathleenae. 



In males, plate of sternite XIV often bearing in- 

 conspicuous anteromedian tubercle; plate of sternite 

 XIII flat, roughly lanceolate, produced in sharp 

 spine, its length 1.5-2.3 basal width. 



Thelycum (Fig. 17) with densely setose plate of 

 sternite XIV short, deeply grooved transversely, its 

 sharp anteromedian margin turned ventrally, plate 

 produced at either side in moderately long, antero- 

 lateral hood; fossa preceding plate long, deep, and 

 bearing pair of small, obliquely disposed ridges. Me- 

 dian plate of sternite XIII, also covered with thick- 

 ly set setae, concave, and produced apically in acute 

 spine; relatively short (length 2.0-2.7 basal width), 

 falling considerably short of spine on sternite XII, 

 broad (maximum width 0.80-0.93 length), and 

 uniquely expanded in strong posterolateral promi- 

 nences continuous with slender ridges extending 

 into fossa of sternite XIV. Sternite XII minutely 

 setose, strongly keeled and crested by median carina 

 ending anteriorly in slender, anteroventrally 

 directed spine. 



The morphological account above is the first to in- 

 clude adult features. This gamba prawn was named 

 by Bate (1888) on the basis of 6 small juveniles, and 

 the characters pointed out by him have proven in- 

 adequate to recognize the species. Subsequent cita- 

 tions to P. gracilis have been based only on Bate's 

 information. The material available to me have 

 allowed the detailed descriptions of the petasma, 

 thelycum, and the ventral flagellum of the male 

 which is unique among the members of Pseudaris- 

 teus. 



Maximum lengths.— Males, 21 mm CL; females, 35 

 mm CL. 



Geographic and bathymetric ranges.— Known only 

 from waters of the Philippines (Fig. 9). It has been 

 taken at depths between 719 and 1,785 m. 



Figure n .—Pseudaristeus gracilis, 9 35.5 mm CL, between Bohol 

 and Siquijor Islands, Philippines. Thelycum. Scale = 2 mm. 



Discussion.— Ferhaps the most conspicuous differ- 

 ence between the males of P. gracilis and those of 

 the other species of the genus of which males are 

 known is in the ventral antennular flagellum, which 

 is sinuous and bears a dense band of closely set setae 

 on the mesial margin of the slightly broadened part. 

 Males also may be distinguished from those of their 

 cogeners by the shape of the dorsolateral lobule of 

 the petasma, which tapers rapidly to the subangular 

 apex and exhibits a setose ventral surface, and also 

 by the ventral costa, which is markedly contracted 

 distally. Characteristic of the females are the short 

 plate of sternite XIV, in which the anteromedian 

 margin is turned ventrally, and the unique strong 

 posterolateral prominences of the median plate of 

 sternite XIII. The prominences are clearly defined 

 in juveniles as small as the syntype with a 10.3 mm 

 CL. 



Pseudaristeus sibogae De Man 1911 



Figures 4£, 9, 18 



Hemipenaeus sibogae De Man 1911:25 [9 holotype, 

 ZMA De. 102.462, E Savu Sea, Indonesia; 

 9°03'24"S, 119°56'42"E; 1,000 m; globigerina; 20 



332 



