SYNOPSIS OF THE BRITISH PHRYGANID^. 59 



and specific characters. The various combinations of the 

 veins are easily intelligible, if we first investigate the simplest 

 and most regular form of the venation {Hydropsyche^, and 

 from this derive the other forms. Close to the anterior 

 margin of the wings runs a strong longitudinal vein, the 

 radius; a finer longitudinal vein, the subcosta, running 

 between the radius and the anterior margin, is of no value in 

 classification. Close to the base two longitudinal veins 

 spring from the radius, the Ramus discoidalis and Ramus 

 thyrifer, which sustain almost the whole of the anterior 

 wing, and in the posterior wings the anterior portion as far 

 as the folded hinder space. These two branches, almost 

 alone, are of importance in classification ; the other veins con- 

 sist of the cubitus with its branches. The Ramus discoidalis 

 and R. thyrifer soon divide, and the anterior branch of the 

 R. thyrifer (the R. thyrifer strictly so called, whilst the 

 hinder branch is called the R. clavalis by Kolenati) divides 

 again. We thus obtain five longitudinal veins, — two belong- 

 ing to the Ramus discoidalis and three to the R. thyrifer. 

 These five longitudinal veins (or a part of them) terminate 

 with a forked cell at the margin of the wing. If, then, 

 transverse veins unite these five cells, the latter with the four 

 intervening spaces constitute nine apical cells. The uniting 

 transverse veins form a straight or broken line, the anasto- 

 mosis. According as the transverse veins unite all the cells, 

 or only some of them, the anastomosis is complete or incom- 

 plete. If a transverse vein unites the two branches of the 

 R. discoidalis, an elongated cell, the discoidal cell, is thereby 

 produced. The anterior branch of the R. thyrifer, a little 

 before its furcation, exhibits a pale perforated spot, the thy- 

 ridium. If we compare the other forms of the venation with 

 this simple representation, they may be easily reduced, es- 



