426 ME. J. R. HENDERSON— A CONTRIBUTION 



antennular peduncles exceed those of the antenna? by nearly half the length of their 



terminal joint. 



The rio-ht or larger chelipede gradually increases in width, as far as the hase of the 

 mohile finger, where it is widest ; the fingers open transversely. The merus has a rather 

 prominent inferior projection. The upper surface of the carpus and propodus is some- 

 what flattened, and armed with not very numerous spinose granules, which are most 

 prominent on the anterior margin of the carpus, bordering the articulation with the hand, 

 and along an area near the middle of the hand surface. The outer margin of the hand 

 is thin and finely serrated, while internally there is a deep or vertical finely granulated 

 surface. The fingers are considerably shorter than the palm and somewhat deflexed, 

 with the mobile one strongly carinated along its inner margin, which is also finely 

 serrated. There are no prominent teeth on the opposing margins of the fingers. The 

 left chelipede is slender, and smooth but for the presence of a few hairs ; its carpus is 

 longer than the hand and fingers taken together. The ambulatory legs are smooth and 

 very sparingly pubescent ; the second pair are unequally developed, that of the right 

 side being longer and proportionately broader than the left, and the two terminal joints 

 are faintly sulcate longitudinally, an arrangement which is not seen on the left side. On 

 both sides the dactyli are longer than the propodi. 



The Australian example, a female, is about 21 mm. long ; the right chelipede (which 

 cannot be fully extended) is 18 mm. long, the left chelipede 14 mm., the second left 

 ambulatory leg 20 mm., and the second right ambulatory leg 23 mm. 



Group Galatheidea. 

 Genus Petkolisthes, Stimpson. 



232. Petkolisthes dentattts (Milne-Edw.). 



Porcellana dentata (Milne-Edw.), De Man, Mergui Crust, p. 216 (1888). 



( = P. bellis, Heller; P. Haswelli, Miers). 



Tuticorin and Muttuwartu Tar {Thurston) ; Pameswaram, common under coral blocks 

 between tide-marks (J. R. H.). 



I have compared my specimens with examples from Mergui examined by De Man 

 and with the types of Petrolisthes Haswelli, and find that all belong to the same species. 

 According to Ortmann, Porcellana dentata of De Man is not the P. dentata of Milne- 

 Edwards, but is synonymous with P. speciosa, Dana ; he seems to have overlooked the 

 fact, however, that the Mergui specimens were examined by Prof. A. Milne-Edwards and 

 pronounced identical with P. dentata, Milne-Edw. The carpus of the chelipedes is 

 usually about twice as long as broad, though sometimes shorter. There is considerable 

 variation in regard to the number and form of the denticles on the anterior and posterior 

 margins of the carpus ; as a rule, there are three on the hind margin. The lobe on the 

 inner margin of the merus is always obtuse. 



Distribution. Nicobars (Heller); Mergui (Be Man); Singapore (Walker); Java 

 (Milne-Edwards) ; Malay Archipelago (De Man) ; N. and N.E. Australia (Miers). 



