210 THE COCKROACH 



veins. They have retained the use to which they were first put, 

 and the changes that have come about, such as the wider expan- 

 sion of the anal area, have been in fuller development of the 

 same purpose ; while the front wings, in virtue of their position 

 in repose, have become more and more protectors of the hind 

 wings, and have gradually lost, in part, if not entirely, their 

 original use. The hind wings of existing Insects, thus pro- 

 tected, have given less play to selective action, and have become 

 to some degree interpreters for us of the more complicated 

 structure, the more modernised anatomy, the more varied 

 organisation of the front wing. 



A third distinction between palaeozoic and modern Cockroaches 

 is found in the veinlets of the anal area. These, unlike the 

 branches of the other veins, do not part from the main anal 

 vein at various points along its course, but form a series of 

 semi-independent veinlets, and in palaeozoic Cockroaches take 

 the same general course as the main anal vein, or " anal 

 furrow' (the curved, deeply sunken vein that marks off the 

 anal area from the rest of the front wins-, both in ancient and 



*-^ ' 



modern Cockroaches), and terminate at sub-equidistant intervals 

 upon the inner margin ; while in modern Cockroaches these 

 veins either run sub-parallel to the inner margin and terminate 

 on the descending portion of the anal furrow, or they form a 

 fusiform bundle and terminate in proximity to one another and 

 to the tip of the anal furrow. 



These differences, which were mentioned bv Germar and 



' / 



Goldenberg, and their universality pointed out in my memoir 

 on Palaeozoic Cockroaches,* seem to warrant our separating the 

 older forms from the modern as a family group, under the name 

 of Palmobla Harm ; this familv has been thus characterised: 



*/ 



Fore wings diaphanous, generally reticulated, and nearly 

 symmetrical on either side of a median line. Externomedian 

 vein completely developed, forking in the outer half of the 

 wing, its branches generally occupying the apical margin ; 

 internomedian area broad at base (be} 7 ond the anal area), 

 rapidly tapering apically, and filled with oblique mostly parallel 

 veins, having nearly the same direction as the anal veinlets, 

 which, like them, strike the inner margin. 



* Memoirs Bost. Soc. Nat. Hist., III., 23 seq. (1880). 



