wi 



th Descriptions of New Forms. 225 



has not been entirely established. Lesquereux, on the evidence 

 of the flora, referred the deposits unhesitatingly to the Permian. 

 Scudder, from a study of the insects, insisted on the Triassic 

 age of the beds. The plants were found to represent several 

 characteristic paleozoic genera. The insects belonged to eight 

 genera, seven of which were cockroaches. Three of the cock- 

 roach genera were otherwise known only in the paleozoic, the 

 remaining genera were new and at that time peculiar to the 

 locality. It may not be out of place to add in this connection 

 that the range of cockroach genera, as understood at the pres- 

 ent time, is much less contradictory to the evidence drawn 

 from the plants than was supposed when the papers in question 

 were written. Five of these seven cockroach genera are now 

 known to occur in the Coal Measures and Permian, leaving only 

 two peculiar to the Fairplay locality and of Triassic affinity. 

 In view of the occurrence as low down as the Coal Measures 

 of the advanced genus Schizoblattina, described above, it 

 would not be surprising to find true Blattida? as early at 

 least as the Permian, and should the fossil here tentatively 

 identified as an egg case, prove to be such, it must be accepted 

 as evidence of the existence of Blattidse along with Paleoblat- 

 tidse as early even as the Upper Coal Measures. Of the Paleo- 

 blattida?, the Mylacridse will doubtless be found the older. 

 The broad pronotum with but slightly rounded posterior bor- 

 der, the greater distance of the subcosta from the costal border, 

 and the presence of a branched submarginal costa in the hind 

 wing, all indicate the earlier position of this tribe. The Blat- 

 tinaria?, on the contrary, are more diversified, continue later, 

 and lead up to more advanced types. 



In the course of their development, the cockroaches afford 

 illustration of laws of evolution which may be summarized 

 under the headings : Specialization by reduction ; parallel evo- 

 lution ; mechanical principle of evolution ; and recapitulation of 

 ancestral characters. 



Specialization by Reduction. — The long ovipositor of early 

 cockroaches seems to indicate that a well-developed ovipositor 

 is a primitive character in the Orthoptera, its reduction in 

 the modern Blattidge being an expression, like the peculiar 

 egg case and genital pouch, of a specialized condition of the 

 external genital organs. In this respect the Gryllidse and 

 Locustidee present, no doubt, a closer approximation to the 

 early condition than do the cockroaches, although on the whole 

 the latter seem to be the more generalized. The more or less 

 complete fusion of two or more of the main veins at their base 

 or throughout a part of their course appears to be a second 

 illustration of the law of specialization by reduction. 



Parallel Evolution in the Orthoptera. — The plication, so 

 constant a feature in the hind wings of modern Orthoptera, is, 



