XXXVlll INTRODUCTION. 



be found sufficieiitly steady in their occurrence to 

 afford safe criteria for classification. 



Prof. Milne Edwards long ago showed that the most 

 reliable characters of some lizards are to be found in 

 such an apparently small matter as the shape of the 

 scales of the head. The import of the scale on the 

 seat of the pineal gland in reptiles, and the theoretical 

 considerations advanced as to its evidence of some 

 sense-organ now in abeyance, may here exemplify how 

 much comparatively small matters may imply, and 

 that they may have really high significance. 



As to the ocelli in Cicadina^, my own experience is 

 that, whilst such organs are sufficiently obvious in 

 genera like Cicadetta and Tcttigonia, in others no ocellus 

 can be detected even by the help of a good microscope. 

 In many species the probable seat of an ocellus is only 

 indicated by a simple spot of pigment. The above 

 remarks, nevertheless, only apply to such British 

 species as have come under my observation. 



CICADINA, Burm. 



Kostrum with two or three articulations rising from 

 the inferior margin of the head. Palpi wanting. 

 Maxillas represented by fine setae enclosed in the 

 rostrum. Antenna constituted of two or three basal 

 joints, terminated by a fine bristle of varying length. 

 This seta or bristle is really formed of numerous small 

 articulations, as seen in the Cercopida3. Eyes two. 

 Ocelli two or three, but often apparently wanting. 

 Elytra deflexed, mostly coriaceous, each composed of 

 the clavis, united to the coreum by a straight and 

 obvious suture. The elytra are disposed over the 

 abdomen pent-wise, each apex developing often into a 

 delicate membranous edge (the linibus), which folds 

 over the commissure when closed, and thus it effect- 

 ively protects the delicate wings which are disposed in 

 many doubliugs within. Hind tarsi three-jointed. 



M. Puton describes the smaller Cicadinse as having 



