iS6 



ARACHNOWEA. 



CASE Atax histrionicus {Hervi. Mem. apt.). — 23. Magnified sketch of male, 

 Arreuurus virldis, Dug. ; 24. Ditto of female, Atax histrionicus, Dug.y 

 copied from figures by Duges, in Ann. Sc. Nat. 1834. 



X, 

 Nos. 



Atax histrionicus (Arrenurus viridis, Di<^.), male. 



Atax histrionicus, female. 



About the size of a mustard seed. 



The male is pale yellowish green, the female a rich purple, with 

 four large black blotches. 



Besides the foregoing, Koch proposes several other genera for 

 species of this group, viz. : 



Nesea, Fiona, Hygrobates,Atractides,Acercus, andMARiCA; 



but neither his figures nor his descriptions are sufficiently precise 

 to allow of our judging as to their value, especially in a family 

 where the general resemblance and the sexual differences are both 

 so great. 



"* Genus Pontarachna {Filippi). 



No. 25. Pontarachna punctulum, FH. — 25. Magnified sketch of ditto, copied 

 from drawing a. d description of Filippi. 



This is a very minute and inconspicuous Hydrachna, with a 

 madder-brown irregular shaped patch covering the back; but 

 it is interesting from its having been found in the sea at Naples, 

 instead of in fresh water. Since then another from the North 

 American Seas has been described by Dr. Packard. Filippi made 

 the separate genus for his species, which we have adopted on his 

 responsibility. 



