112 THE VOYAGE OF H.M.S. CHALLENGER. 



lines ; tlie dactyli are short and moderately curved, each terminating in a yellow horny 

 claw. 



The abdominal segments are smooth and polished externally. 



Breadth of carapace 4 "5 mm., length of carapace 5 mm., of extended abdomen 5 mm., 

 of chelipede 6'5 mm., of second ambulatory leg 6 mm. 



This small species owes its chief interest to the depth at which it occurred — one which 

 is quite exceptional among the members of this group. Apart from the difference in size 

 it bears some resemblance to the common European Porcellana platyclielcs (Pennant), a 

 young sj)ecimen of which from Millport, Fii'th of Clyde, is figured beside it (PL XL 

 fig. 7); the Challenger species, however, possesses a less prominent frontal region, shorter 

 chelipedes and ambulatory limbs, and the lobe on the inner margin of the carpus is larger 

 and less pointed. I have pleasure in naming it after my friend Mr. David Robertson, 

 the veteran naturalist of the Clyde district. 



Habitat. — Station 24, ofi' Culebra Island, West Indies ; depth, 390 fathoms ; bottom, 

 Pteropod ooze. A female specimen. 



Genus Porcellanella, White. 



Porcellandla, White, in Macgillivray's Voyage of H.M.S. "Rattlesnake," vol. ii., Appendix, 

 p. 395, 1852 {sine deser.). 

 „ Stimpson, Proc. Acad. Nat. Sci. Philad., p. 67, 1858. 



Carapace oblong, the length considerably greater than the breadth, with the lateral 

 borders almost parallel, and the gastric elevations obsolete. Front prominent, composed 

 of three flattened horizontal teeth. First joint of the antennal peduncle elongated and 

 acute. Chelipedes smooth, with the carpus short and the propodus elongated. Ambula- 

 tory limbs of small size, with the meral joints robust, the dactyli short, compressed, and 

 multiuna;uiculate. 



This genus approaches Porcellana somewhat closely in its characters. Stimpson 

 described a second species, Porcellanella picta, from the Chinese Seas. 



Porcellanella triloba, White. 



Porcellanella triloba, White, in Macgillivray's Voyage of H.M.S. "Rattlesnake," vol. ii., 



Appendix, p. 394, pi. v. fig. 2, 1852. 

 Porcellana triloha, Haswell, Catal. Austral. Crust., p. 149, 1882. 



Habitat. — Station 212, Celebes Sea; depth, 10 to 20 fathoms; bottom, sand. 

 Several specimens, two of which are females with ova. 



Station 315, Port WiUiam, Falkland Islands; depth, 5 to 12 fathoms ; bottom, sand, 

 gravel. A male specimen. 



This species has hitherto been recorded only from the Australian coasts ; it has, 



