NLI IIOI'THRA. 93 



This table brings to light some curious discordances when the species 

 from the American and European rocks are compared. This indeed is 

 marked in every instance where the numbers are considerable on either side, 

 excepting- in the Termitina, where we have six American to ten European 

 species. Europe shows a decided superiority in theOdonata, where thirty- 

 t'nTir species are offset by only eleven species in America; and it is not 

 a little curious (though not unexpected, considering the nature of the 

 deport ) that it is here only that the amber fauna adds scarcely at all to the 

 European preponderance. The American Thysanura find no counterpart 

 in the European rocks, though the amber fauna counts no less than twenty - 

 eight species, while the American representatives of the Ephemeriiia (six 

 species), the Planipennia (twelve species), and the Trichoptera (twenty -five 

 >pfcii--.) far outweigh the European examples, Ephemerina (one species), 

 Planipennia (six species), Trichoptera (seven species). This American 

 preponderance is in every instance counterbalanced when the total Tertiary 

 yield of Europe is brought to view, the Ephemerina showing seven species, 

 the Planipennia nineteen species, and the Trichoptera forty species. 



If the smaller groups are considered, there are some closer correspond- 

 ences, as when we find eight species of American Agrionina to ten in the Euro- 

 pean rocks, two American to one European Hemerobida? and Panorpidae, two 

 American to t\vo European Limnophilidae, and four American to five Euro- 

 pean Phryganidae. The discrepancies, however, are not less marked, for 

 we find of groups unrepresented in European rocks four species each of 

 Kaphidiidie and Chrysopidse, seventeen of Hydropsychidae, and two of 

 Leptoceridae in American strata, which in the first two instances are hardly 

 or not at all represented in amber. On the other hand, the European 

 rocks show species of Calopterygida? (one), Gomphidse (three), Cordulidae 

 (two), Sialidse (one), Ascalaphina (two), and Myrmeleontidse (one), where 

 the American rocks are wholly destitute. On the whole, the European 

 rocks, as compared with the American, are rich in Odonata and poor in 

 Ephemerina, Planipennia, and Trichoptera. While, if the entire Tertiary 

 yield of Europe is considered, America nowhere shows a considerable pre- 

 ponderance of forms excepting in the small planipennian groups of Raphi- 

 diida? and Chrysopidae, while Europe has a very striking preponderance in 

 Thysanura, Psocina, Perlina, ^Eschnina, Libellulina, and Hemerobida?, 

 having in none of these cases less than four times as many species as 

 America. (February, 1884.) 



