S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 25 



Div. a. Reticulation tetragonal ; main veins free. (9 species.) 



Div. b. Main veins connected at the base. (1 species.) 



Div. c. Reticulation polygonal ; main veins free. (2 species.) 



Div. d. Hind wings. (2 species; one wrongly placed here.) 



The only other classification which has been attempted is that recently made by Golden- 

 berg, 1 which is merely an extension of Heer's. He first separates those of the true carbon- 

 iferous series from those occurring in the dyas, and for the former offers the following 

 scheme : 



f with simple quadrangular cells arranged 



f fore- wings membranous f principal < in rows; Group I. (II sp.) 



W o-^l • ' with distinct venation; < veins free; ( with polygonal cells; Group II. (18 sp.) 

 ° ' j ( principal veins connected at the base ; Group 111. ( 1 sp.) 



{ fore wings coriaceous, with indistinct venation ; Group IV. (1 sp.) 



Wingless ; Group V. (1 sp.) 



The few species from the dyas are divided into that from Weissig (1 sp.), and those 

 from Lebach (2 sp.), and the latter are placed severally in groups corresponding exactly to 

 Groups n. and III. of the carboniferous series. 



Nearly all the species represented by fore-wings, whether in the classification of Heer or 

 of Goldenberg are grouped, then, according to whether the minute cross-venation or reticu- 

 lation of the wings is composed of polygonal cells or simply of cross veins running directly 

 from one nervule to another. There are three serious objections to the naturalness of such 

 a classification. First, it assigns a high importance to a necessarily insignificant feature in 

 the structure of the wing. Second, the reticulation is frequently invisible either from its 

 actual absence or the imperfect preservation of the fossil. And third, the same wing 

 exhibits, certainly in some American species (e. g., Etobl. venusta, E. Lesquereuxii), a trans- 

 verse reticulation in one part of the wing, and a honeycombed reticulation in another. 

 We may therefore fairly set aside these classifications as insufficient and unsatisfactory. 



More than ten years ago, in studying the first fossil cockroaches that 'came under my 

 observation, and noticing the diversity of structure in the wings of palaeozoic species, 

 I described two types under new generic names ; but on the discovery and separate descrip- 

 tion of additional forms, it seemed best to revert to the common custom of referring all to 

 Blattina until the present revision or some other was attempted. 2 A considerable number 

 of new and interesting forms having recently accumulated, it seemed a favorable oppor- 

 tunity to pass the entire series under review ; accordingly the illustrations of the described 

 European species were copied and brought, as given in the plates, to the same scale 

 (X 2 diam.), and, when necessary, so reversed as to place the costal margin on the left, the 

 base of the wing being uppermost. This renders comparison more direct and simple, and 

 in such as have been reversed it is merely the same as if one looked at the wing from the 

 opposite surface. 



A comparison of these with American types at once showed that, among the latter at 

 least, a remarkable degree of diversity obtained, necessitating the division of the palaeozoic 

 cockroaches into two tribes, according to the structure of the uppermost vein of the front 

 wing : this vein, in one tribe, exclusively American, being composed of a series of long 



1 Golilenbcrg. Fauna saraepontana fossilis. Huft 2, pp. - Canad. Naturalist (2) vii, 271. 



18-20. 4°. Saarbriicken, 1877. 



