1(52 Mr. R. Slielford on new 



alar organs is much simplified and approximates to a radiate 

 type, there being but little branching of the veins. The 

 minute tarsal claws constitute another higlily remarkable 

 character. It is difficult to discover the affinities of a genus 

 so aberrant as this ; the biseriate arrangement of the tibial 

 spines shows that it must be placed in tlie section of the sub- 

 family which embraces Latindia, Stal, Paralatindia, Sauss., 

 Ilomopteroidea, Shelf., &c. ; but it cannot be regarded as 

 closely related to any known genus. 



S ubf a m . Perisfh^riin^. 

 The Form of the Pronotum in the Perisphffiriinjfi. 



De Saussure and Zehntner, in their revision of the Peri- 

 sphaeriinge (Rev. Suisse Zool. vol. iii. 1895), have traced the 

 evolution of the complex type of pronotum of such genera as 

 Pilema and Cyrtotria [= Stenopilema, Sauss.] from a simple 

 type. A summary of their conclusions may be presented 

 here, and I have added some diagrammatic figures as a help 

 to its elucidation. In a typical Blattid pronotum two areas 

 may be distinguished, the disk and the lateral wings, which 

 project on either side beyond the outer limits of the pro- 

 sternum ; the disk covers the head and on the underside is 

 more or less defined by a pair of carinje, known as the typical 

 carinas. In transverse section this form of pronotum may be 

 represented as in PI. IX. fig. 10, A, where a represents the 

 disk, bb the lateral wings, and cc the typical carina. In tlie 

 genus Pronaonota (PI, IX. fig. 10, B) the lateral wings are 

 strongly bent downwards and an incomplete carina [d] on 

 the deflected sides of the dorsal surface of the pronotum 

 foreshadows the separation of the lateral wings from the disk. 

 The separation is more or less complete in the genera Pilema 

 and Cyrtotria (PL IX. fig. 10, C) ; the lateral wings in 

 these genera now appear in side view as lateral bands bent 

 down at a right angle, or at more than a right angle, to the 

 disk of the pronotum, and their upper (morphologically inner) 

 border is elevated, so that in dorsal view it appears as if the 

 lateral borders of the pronotum had been simply reflected 

 from below upwards. Such, liowever, is not really the case ; 

 tlie carina on the pronotum of Pronaonota is the morphological 

 equivalent of the upper edge of the lateral band of Pilema, 

 and the lateral margin of the pronotum of Pronaonota is the 

 equivalent of the lower edge of the lateral band of Pilema. 

 This lateral band is morpliologically the lateral wing of the 

 pronotum, which has become divided off from the disk. 



