NEUKOPTEKA. 91 



IN^EUI^OF'TER^ Limits. 



Using this term in its large sense, us, tor convenience, we have done 

 here, there is no group of fossil insects more interesting. In no other, 

 unless it be the cockroaches among Orthoptera, do we find a considerable 

 representation in all the rocks which have yielded fossil remains Still the 

 time has, perhaps, not yet come for a careful historical survey of the group, 

 since we are annually receiving large additions to our knowledge of the 

 extinct types, and a considerable number of those known have been insuffi- 

 ciently studied. Such a study, too, belongs essentially to the student of 

 the older types, and would be less appropriate here, for it may certainly be 

 stated with confidence that the types of existing Neuroptera were thor- 

 oughly established at the beginning of the Tertiaries. With a single excep- 

 tion, Ballostoma, no large group existed theii and has since expired, nor is 

 there a single existing type of any prominence which has not been found in 

 the Tertiaries, unless we look upon the aberrant and until lately hardly 

 known Scolopendrella as belonging here. Yet a large proportion of the 

 genera of Tertiary Neuroptera are extinct ; that is, differentiation has gone 

 on with the lapse of time, until the original characteristic features of an 

 early group have been lost and new ones taken their place, and no species 

 referred to in the following pages exists at the present time. The differ- 

 ences between tlie Tertiary and existing forms are never very great, usually 

 rather small, but they are constant and everywhere found. 



The number of known Tertiary Neuroptera is considerable. For the 

 sake of gi-aphic comparison I have presented the facts as far as possible in 

 the following table, where, in the European colunms, the numbers at the 

 right are the real total, the others representing those known from the rocks 

 alone (excluding the amber) for the sake of comparing more fairly the yield 

 of the European and American rocks. The numbers on the American side 

 represent with a single exception (Phryganea hyperborea from Greenland) 

 the result of my own studies only, and therefore the numerical estimate is 

 presumably more correct than in the European; in the latter I have 

 endeavored to give a fair statement of the numbers, including a considera- 

 ble proportion of mere indications, the value of which had to be weighed, 

 sometimes in a somewhat summary manner. 



