208 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 24 



troisieme, quatrieme et cinquieme articles de la troisieme paire de 

 pattes [outer maxillipeds], comprimes et dilates interieurement ; le 

 sixieme alonge en triangle; la quatrieme paire de pattes [chelipeds] 

 comprimee." In species belonging to Porcellana, according to Leach, 

 the third article of the outer maxillipeds is cylindrical, the fourth and 

 fifth dilated exteriorly. Desmarest (1825, p. 197) pointed out that 

 Leach's characterization of Porcellana was in error, the form of the 

 outer maxillipeds being not as described by the latter author but on 

 the contrary as in Pisidia ; while following Leach's classification, he 

 believed that Pisidia should be suppressed since the two genera could 

 not be separated on the basis of the characters given. The name Pisidia 

 has been practically ignored by subsequent writers, including Stimpson 

 (1858) in his synopsis of the porcellanid genera. 



Leach designated no type for Pisidia, in which he included species 

 now placed in at least three genera. In order that the name may be 

 applied to the group of species here separated from Porcellana, Pisidia 

 Hnnaeana L,each = Porcellana longicornis (Linnaeus), 1766, is hereby 

 designated the type of Pisidia. 



Czerniavsky (1884) characterized his new genus Porcellanides as 

 having multiunguiculate dactyli as in Polyonyx Stimpson and Porcel- 

 lanella White. From his illustrations of specimens from the Black Sea, 

 however, it is evident that the dactyli do not have two or more strong 

 fixed spines as in those genera, but rather a single spine and several 

 small accessory spinules ; from this character and others described by 

 Czerniavsky, Porcellanides is clearly a synonym of Pisidia in the pres- 

 ent sense.^ (It should be noted that the type species, Porcellanides 

 kriczagini Czerniavsky from Singapore, was very briefly described 

 and was not figured. Judging from the short description it is perhaps 

 a synonym of Pisidia spinuligera (Dana), 1853; but until its status 

 can be determined, Porcellanides can only provisionally be considered a 

 synonym of Pisidia.) 



Stimpson (1907, p. 188), as mentioned above, recognized this group 

 of species: "A group of small species [of Porcellana^, with one of the 

 hands much twisted and its fingers excavated, shows some other dif- 

 ferences which serve to distinguish it from the typical group founded 

 on the P. platycheles and similar forms. They might form a distinct 

 genus (to which the name Streptochirus would be applicable), but they 

 are so intimately connected with the others in the more essential char- 

 acters that it is thought best not to separate them here." The name 



1 Cf. Makarov, 1938, pp. 106-107. 



