194 A HISTORY OF RECENT CRUSTACEA 
others of this family, the basal joint of the second antennz 
is not free, but closely fused with the ventral portion of 
Fia. 16.—Jbacus incisus (Peron) [Desmarest]. 
the head. Spence Bate enumerates twenty-two pairs of 
branchize in this species. Why he caanges Lbacus into 
Ibaccus he has not bequeathed us any explanation. 
Pseudibacus Veranyi, Guérin, may receive a passing 
mention, as a Mediterranean species. 
Arctus, Dana, 1852, has the rostrum very short and 
truncate, the second antenne remote from one another, 
the exopod of the third maxillipeds without a lash, and the 
pairs of branchize nineteen in number. 
In the definition of this genus Dana is practically fol- 
lowing de Haan in stating that the palp of the third 
maxillipeds is without a flagellum. Mr. Spence Bate 
translates this into his own terminology, and speaks of the 
genus ‘ having no ecphysis attached to the second pair of 
gnathopoda, which would mean that there was no exopod 
to the third maxillipeds at all. But that is not the case. 
