802 



ARTHEOPODA 



PHYLUM VII 



From this generalised stock have probably been derived a numl)er of more 

 specialised families, also limited to the Paleozoic (Upper Productive Coal Measures 



and Permian), among ■which may 



\.Anal Veins 



MediaslinaL 

 Scapular - 

 E:rtemomedicax 



-Jtnal Furrow 

 Interiwmedian 



be mentioned the following : 



Spiloblattinidae, with smooth 

 fenestrated spaces between the bor- 

 dered longitudinal veins of the 

 tegmina ; Mylacridae, with the sub- 

 costal branches given otf from a 

 common point of origin at the base 

 (Fig. 1548, G); Poroblattinidae 

 and Neorthroblattinidae, with a 

 very short subcosta ; Mesoblatti- 

 nidae, with the subcosta forming 

 only a callous at the base of the 

 anterior border ; Pseudomylacridae, 

 Dictyomylacridae, Neomylacridae, 

 Pteridomylacridae, Idiomylacridae, 

 Diechoblattinidae, and Protere- 

 niidae. 



Tertiary cockroaches are all 

 referable to modern families, and 

 are probably descended, at least for 

 the greater jjart, from the Mesoblattinidae, a family which is abundantly rej^resented 

 in Jurassic rocks. Many larval forms and even egg packets of cockroaches are found 



Fig. Ii47. 



Neuration of one of the tegmina of a Paleozoic Cockroacli 

 Asemohlatta mazona (Scud.), from the Coal Measures of Illinois. 

 The veins are named at the bnse of the tegmen, and the areas 

 are marked along the margin, -/i (alter Scudder). 



Fui. 1548. 



Types of fore wings in Paleozoic Cockroaches, "j-^. A, Priiriitive Archimylacrid. V,, Jlore highly specialised 

 Archimlyacrid. (\ Mylacris, typifying the Mylacridae. Nervures are marked as in Fig. 1531. 



fossil. Specific determinations are often difficult, no two individuals being exactly 

 alike, and difterences often existing between the right and left wings of the same 

 individual. 



