112 PROCEEDINGS OF THE ACADEMY OF [1885. 



unnamed. Giebel two years later named a considerable propor- 

 tion of Brodie's and Westwood's species ; while placing a con- 

 siderable number under Blatta and Blattina, he divided the rest 

 •under three new genera, Bithma, Elisama and Nethania, the last 

 including the only one of Westwood's species of Blattidium which 

 was noticed. On the other hand, Heer, in 1864, divided all the 

 mesozoic species between Blattina and Blattidium, placing in the 

 latter all of Westwood's species, together with all those referred 

 to new genera by Giebel. Finally, a few years ago E. Geinitz 

 proposed for a triassic species described by him, and one pre- 

 viously published by Heer, the new generic term Mesoblattina. 



There is no question that the forms described by Westwood, 

 after eliminating the one separated by Giebel, under the name of 

 Nethania, form a very distinct group ; but none of the species 

 since added to it belong here, so that 



BLATTIDIUM 



should stand much as first limited (though not described) by 

 Westwood. Probably, however, it should be still further 

 restricted by the elimination of B. Achelovs Westwood. The 

 wings are exceedingly long and slender, particularly in B. 

 Symyrus Westw. — which may be taken as the type — with nearly 

 or quite parallel sides. The mediastinal vein terminates not far 

 from the middle of the wing, and sends out a multitude of 

 crowded offshoots to the margin. The scapular vein unites in the 

 basal third of the wing with the externomedian, and throws off 

 rather distant oblique veins, first to the mediastinal, and after- 

 wards to the border. The externomedian and internomedian 

 veins have together several more or less forked, very longitudinal 

 branches, all of which appear to terminate on the apical margin, 

 while the main anal vein, longitudinally oblique, extends nearly 

 as far as the mediastinal, and the outer half of the inner margin 

 of the wing seems to have no veins falling upon it ; the veins of 

 the anal area run obliquely from the margin upward and outward 

 to the main anal vein. 



As to the genera of Giebel, six species are placed by him in 

 Bithma, two in Elisama and one in Nethania. The species of 

 Nethania is rather too uncertainly figured to determine by the 

 illustration alone where it belongs. The two species of 



