1 | L ' SAMUEL II. SCUDDEK ON 



Oolites. The genera peculiar to the upper Oolite are however very poor in species, one 

 having - only on i and the other only two representatives, while the genera common to the 

 Lias and Oolite arc generally prolific in this respect. 



Of the seventy-seven species of Blattariae mentioned in the following- pages, not in- 

 cluding those found in the Appendix:, three are found in the Trias, seventeen in the Lias, 

 three in the mid He Oolite and forty-six in the upper Oolite, besides three whose precise 

 horizon is unknown. 



A comparison of the venation of the tegmina of mesozoic and recent cockroaches, to 

 determine, as far as possible, the immediate relations of the former to existing forms, 

 gives little satisfaction. Still, Mesoblattina and Rithma may be said to hear considera- 

 ble resemblance to the Phyllodromidac — as Phyllodromia, Apolyta and Thyrsocera, for 

 examph — and the peculiar neuration of Elisama is in part repeated in the Panchloridae 

 (e. g., Panchlora, Leucophaea, Nauphoeta) and also occurs in some Phyllodromidac 

 (Thyrsocera) and Epilampridae (Paratropa, Epilampra). Scntinoblattina also reminds 

 one in certain features of same Epilampridae, like Phoraspis. The other genera, and 

 particularly Blattidium and Pterinoblattina, appear to have no relations to any special 

 type. As a whole, then, it would appear as if the Blattariat spinosae approached closer 

 to the mesozoic forms than the Blattariae muticae. 



As I have already stated, the most fundamental distinction separating the mesozoic 

 from the paleozoic cockroaches is in the change which the principal nervures of the upper 

 wings have undergone, by the basal or total amalgamation of some of them, — a change 

 which reaches its culmination in living cockroaches. 



On the basis of these differences, mesozoic cockroaches may be divided into three 

 groups: a, tho>e in which only the mediastinal and scapular veins are amalgamated; 

 I), those in which the externomedian is united with one of the veins on either side of it; 

 and c, those in which either the mediastinal, scapular and externomedian veins are all 

 united: or there are two lines of union, one between the mediastinal and scapular, and 

 the other between the externomedian and internomedian veins, i.e., where, besides the 

 union of the mediastinal and scapular veins, the externomedian also allies itself in whole 

 or in part with the united mediastino-scapular, or with the internomedian. In all meso- 

 zoic cockroaches, excepting the Triassic Palaeoblattariae, amalgamation of some of the 

 veins occurs; for a further study of Pterinoblattina convinces me that my first interpre- 

 tation of its neuration was incorrect, in that what I had taken for the internomedian 

 vein is really the anal, and that what was looked upon as the externomedian must be 

 regarded as the united externomedian and internomedian veins. 



-&■ 



a. The mediastinal anil scapular reins of the upper wings, and these only, 



are amalgamatt </. 



CtENOBLATTINA gen. now {xnvmruq). 



In the wings of this group, which are minute, the humeral angle, usually consider- 

 ably developed in cockroaches, is obliquely docked, and the united mediastinal and scap- 

 ular veins occupy a broad area, at firsl nearly one-half of the breadth of the wing, and 

 extend nearly to the tip, provided with numerous parallel more or less forking branches. 



