118 OKHAMANDAL MARINE ZOOLOGY REPORT 



be distinct from P. tuherculosus. The ambulatory daetyli of the last species are 

 not described by de Man. I have noticed in one or two specimens of P. obesulus 

 a slight tendency towards tuberculation of the hand, chiefly in young individuals, 

 but our species may be distinguished from this variety by the greater tuberculation 

 and the difl"erent ambulatory daetyli. De Man had only a single small specimen, 

 and it may have belonged to this variety of P. obesulus, in which case a new 

 name will be necessary for the form, which is here briefly characterised." 



Unfortunately, I have been unable to obtain de Man's description of P. tuher- 

 culosus, but the complete tuberculation of the carpus, and propodite, of our specimens, 

 would almost alone be a point of sufiiQient distinction between the two specimens. 

 Many individuals of P. hendersoni, n. sp., were examined, and the tuberculation of 

 the carpus and propodus were found constant in every specimen. In one specimen 

 the dactylus of one of the thoracic legs bore four small proximal spines instead of 

 two. There can be little doubt, however, that P. hendersoni, n. sp., is a quite 

 distinct species, and I have pleasure in naming it in honour of Dr. J. R. Henderson, 

 who first described it, and whose careful work on the Anomura in general is so well 

 known. 



Petrolisthes, Stimpson. 



Stimpson (34), Miers (26), Haswell (14), Henderson (19). 



Characters of the genus : — 



Carapace subovate, depressed, the length shghtly greater than the breadth. 

 Frontal region triangular, usually depressed, with the antennal peduncle remarkably 

 short. Chelipedes broad and flattened, the carpus of moderate length, and often 

 provided with teeth on the inner margin. Ambulatory limbs with the daetyli short and 

 robust, terminating in a single claw. 



Petrolisthes bosci (Audouin). 



Porcellana boscii, Heller (15). 

 Petrolisthes boscii, de Man (25). 

 Porcellana rugosa, Milne-Edwards (9). 



The front is prominent, triangular and deflexed, presenting a median furrow. The 

 carapace is depressed, and slightly longer than broad. Margins entire and terminating 

 anteriorly in an acute epibranchial spine. The surface is marked by a very noticeable 

 mosaic, and by the strong development of granulate, filigerous, elevated, irregular lines, 

 which are visible to the naked eye. Chelipedes equal, and beautifully sculptured like 

 the carapace. The merus is armed with three spines at its distal extremity, one 

 internal, one external, and one ventral and median. Carpopodite armed internally 

 with a varying number of large spines (usually three or four), and externally with a 



