South African Crustacea,. 41 



some doubt P. armatus (Dana). This arrangement was accepted 

 by Bassett-Smith in 1899, but rejected by C. B. Wilson in 1907, 

 who separated Dana's species under the new generic name of 

 Pholidopus. All the available information appears to be derived 

 from Dana, whose report seems to depend on a single specimen 

 of the female sex, a third of an inch long, without egg-strings. 

 Under the circumstances it is allowable to suggest that Dana 

 may have made mistakes in the minute and difficult details 

 which separate PholiJopus from Achtheinus. Thus, he repre- 

 sents the third and fourth pairs of feet as alike having the 

 rami one-jointed, but he only figures separately one of these 

 two pairs, and may have taken for granted that the third was 

 like the fourth. He records the first pair as uniramose, but 

 these minute limbs might easily have lost one of the branches 

 in the process of dissection. In Achtheinus all four pairs of feet 

 are biramose, and only the fourth pair have the rami one-jointed. 

 Since, however, Wilson has now instituted Achtheinus with well- 

 ascertained characters, the merely conjectural identity of Pholi- 

 dopus may stand aside. 



It should be noticed that Wilson in his account of Achtheinus 

 dentatus says, " The present specimens agree in every generic 

 particular with the type species A. oblonyus." Still, in diagnos- 

 ing the female of the latter he says, " Genital segment much 

 smaller than the carapace," whereas in A. dentatus it is much 

 larger than the carapace. 



ACHTHEINUS DENTATUS, Wilson. 

 Plate XCVII. 



1911. Achtheinus dentatus, Wilson, Proc. U.S. Mus., vol. 39, p. 630, 



pi. 67, figs. 22-31. 



The female sex has been fully described by Wilson, whose 

 figure shows the relative length and breadth of the carapace 

 more accurately than mine does, which from a depression of the 

 front disguised the true length. This is in fact somewhat 

 greater than the breadth. 



One male was found in close attachment to the underside of 

 a female. The carapace is more than twice as broad as the 

 following segments and longer than the whole five of them 

 together. Of these the first three combined are little longer 

 than the fourth, which equals them in breadth and is more 



