FISHERY BULLETIN: VOL. 85, NO. 2 



through the kindness of A. Crosnier, who discussed 

 this shrimp in his work of 1984. He pointed out 

 features that he beheved would distinguish it from 

 P. crassipes and P. sibogae: the absence of setae 

 from the integument; a narrower median plate on 

 sternite XIII (Fig. 13); the absence of setae on the 

 pereopods [ typically present in P. sibogae but lack- 

 ing in P. crassipes]; and a robust optic calathus 

 which resembles that of P. crassipes. 



The Indonesian specimen definitely does not 

 belong to P. sibogae, but its relation to P. crassipes 

 is not entirely clear. A few specimens of the latter 

 species are glabrous, a condition, as noted by 

 Crosnier, unlikely to have been attained acciden- 

 tally, but absence of setae is not typical of any 

 species of the genus. Variations in the length/width 

 ratio of the optic calathus of P. crassipes embrace 

 that of the Indonesian specimen, the mesial margin 

 length of which is equal to the distal width. The max- 

 imum width of the median thelycal plate of sternite 

 XIII in most females of P. crassipes ranges from 

 0.50 to 0.55 its length (in one setose specimen, 

 Figure 12B, however, it is only 0.47), whereas the 

 maximum width, 0.45, falls below this range in the 

 Indonesian female. The latter exhibits on the plate 

 of sternite XIV a median ridge that ends in a minute 

 anterior spine, the plate is not produced at either 

 side in an anterolateral hood, and the contour of the 

 median plate on sternite XIII is almost uniformly 

 broad from the base to about midlength. These 

 features differ from those of typical P. crassipes 

 females in which the plate of sternite XIV is un- 

 ornamented, a well-developed anterolateral hood is 

 produced at either side, and the contour of the me- 

 dian plate on sternite XIII broadens from a narrow 

 base posterior to its midlength, then tapers to its 

 apex (cf. Figs. 12, 13). Additional material from the 

 Indonesian locality, including males, might provide 

 evidence for assigning this form to a new taxon. 



Discussion.— The males of P. crassipes differ 

 strikingly from those of its congeners in that the 

 ultimate article of the third maxilliped is twisted 

 (forming a strong concavity laterally), conspicuously 

 expanded proximally, weakly to markedly dilated 

 distally, and studded with minute spines ventro- 

 laterally. The petasma differs from that of P. 

 kathleenae and P. gracilis, the other 2 species for 

 which adult males are known; the dorsolateral lob- 

 ule is not expanded distolaterally, as it is in the 

 former, and it tapers gently to a broadly obtuse apex 

 instead of narrowing rapidly as it does in P. gracilis. 

 Furthermore, the ventral costa turns somewhat 

 abruptly distomesiad rather than forming a gentle, 



Figure \2,.—Pseudaristeus crassipes, 9 35 mm CL, Strait of 

 Makassar, Indonesia. Thelycum. Scale = 2 mm. 



sinuous curve or simple arc, and, in contrast to the 

 costa of P. gracilis, its terminal part, which is also 

 truncate as it is sometimes in the latter species, is 

 not set off by a conspicuous constriction. 



The females of P. crassipes can be distinguished 

 readily from those of P. kathleenae by the shape of 

 the third article of the antennular peduncle, which 

 in the former is uniform in width proximally and 

 tapers distomesially, but in the latter is expanded 

 laterally in a broadly rounded prominence. Also, 

 although the thelyca of these 2 species exhibit a 

 marked resemblance, the median plate of sternite 

 XIII is narrower in P. crassipes than that in P. 

 kathleenae, its maximum width ranging from 0.45 

 to 0.55 instead of 0.67 to 0.75. 



Remarks.— In the original description of Aristeus 

 crassipes, Wood-Mason (1891) cited two females, 

 one from Investigator station 116 and another taken 

 at lat. 6°29'N, long. 79°34'E [off southeastern Sri 

 Lanka], perhaps collected by the Investigator. He 

 did not designate either specimen as the holotype 

 and consequently they must be considered syntypes. 

 Later, Alcock (1901b) recorded the registration 

 numbers of the various lots of specimens of this 



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