320 SAMUEL II. SCUDDEfc ON THE 



this discovery following close upon my demonstration that ;ill paleozoic cockroaches 

 belonged to a type distinct from and taxonomically equivalent to existing Blattariae, lends 

 countenance to a new attempt to discuss the relationship of all paleozoic hexapods to each 

 other and to later types. The time has plainly come for a revision of our general knowl- 

 edge in the light of special discoveries. 



Our acquaintance with paleozoic hexapods is mainly based upon the structure of the 

 win^s, and this is greatly simplified by the fact that, as has been previously noted, differ- 

 entiation in the structure of the front and hind wings of insects had not in paleozoic times 

 obscured the neural framework of the front wings. It is nevertheless tine that the great 

 advances in our knowledge of relationships among paleozoic insects have not come from a 

 study of the wings, but from the happy and rare discoveries of other parts of the 

 bodily structure, as in Eugereon and Protophasma. This would be supposed to render 

 any attempt to reduce the entire series to systematic order somewhat hazardous, were it 

 not that, as will appear later, the great body of forms now known can be grouped, by 

 their wing structure, into a few distinct types, whose relation inter se is such as to warrant 

 a belief that they must have been structurally related in the rest of their organization; 

 and that, among the forms so related, one or another has generally preserved such frag- 

 ments of the body as enable one to speak with some degree of confidence ; at the same 

 time it will have to be admitted that while we are dealing with imperfect remains, any 

 deductions which may be drawn from inferred structure is valuable only a< it is 

 cumulative. 



Brongniart in his latest papers, while, as stated above in a note, unnecessarily anil 

 undesirably dropping the name Palaeodictyoptera, — a name historically connected with the 

 greatest advances in our knowledge of the relationship of paleozoic insects, — has also 

 extended its scope, so as to include also all the forms he (and others) had previously 

 placed under Neuroptera and Orthoptera, but, impliedly, leaving the species of Fulgorina 

 still under Hemiptera. There is no reason for this exclusion, and it is probable that it was 

 not intended. 



Leaving aside, for a moment, the question of the existence of paleozoic Coleoptera, we 

 submit that the same reasons which would justify the use of the term Palaeodictyoptera 

 for Eugereon alone, as was done in the first instance by Dohrn (for its predecessor Dietv- 

 optera), compel us to include in it the entire series of paleozoic hexapods. It is a name 

 too which is peculiarly appropriate to the insects of the paleozoic epoch as a whole, with 

 their undifferentiated wings. It is as applicable to the ancient ephemerids as to the 

 phasmids or cockroaches, and any definition of it grounded on known characteristics must 

 be based almost wholly upon the structure of the wings, from which the name is derived: 

 this structure is, collectively, so simple, the similarity between representatives of groups 

 whose descendants are afterwards ordinally distinct so striking, that we may be justified 

 in claiming the probability of the homogeneity of other parts of their structure. At all 

 events the known facts of the structure of paleozoic insects, apart from the historic develop- 

 ment of the hexapod type in subsequent epochs, would warrant no ordinal separation 

 between them. In saying this I do not overlook the fact that Eugereon was probably a 

 sucking, and Protophasma a biting, insect, for a physiological distinction is of itself of no 

 value whatsoever; it is the underlying structure only that should be considered ; and we 



