128 HORTENSE BUTLER. 



Neurobasis the cleft is much deeper, extending far below the bases 

 of the lateral lobes, and becoming lozenge shaped. The two small 

 seta) are placed near the top. It seems very possible that these setae 

 may be land-marks indicating the situation of the sutural line, which 

 has been mentioned so many times previously. In all excepting the 

 Phaon the border of the ligula is covered witii minute teeth. 



Agreonin.e. — Hyponeurw lagens (PI. V, Figs. 7 and 8) offers a 

 marked contrast to the members of the group above described. The 

 lateral lobe is not very different, although only two hooks appear 

 below the movable hook. There is a single seta on the lateral lobe. 

 The ligula, however, is without a cleft and is covered across its 

 entire border with small hairs. Podagrion sp. ? (PI. V, Fig. !•) 

 exhibits a small cleft in the ligula, the lateral lobe is very similar to 

 that of Hyponeura, but the seta is absent. The latei'al \ohe of E)ial- 

 lagma doubledayi (PI. V, Fig. 10) shows between the movable hook 

 and the end hook four small but clearly defined teeth. Five setje 

 appear along the outer edge. 



Lestin^. — From the lateral lobe of Enallagma to that of Lestes 

 iincata (PI. VII, Fig. 11) the transition is easy, especially in the 

 light of the ontogeny of the lattei". Lestes has a large, incurved 

 end hook and above it, separated from it by a deep cleft, is a series 

 of eight teeth ; the two outer ones of this set are much larger and 

 divaricate. The movable hook is well developed and bears two or 

 three (generally three) large setse, while one appears upon the lat- 

 eral lobe just before the hook. The inner edge of the lateral lobe is 

 bordered by a series of small teeth. Archilestes grandis (PI. V, 

 Fig. 12) has an end hook similar to that of Lestes, but between it 

 and the movable hook appear only two large teeth. These are 

 probably homologous witli the two outer teeth of the set in Lestes. 

 Two setie appear (jn the movable hook and one large one, and two 

 spinules on the lateral lobe immediately below it. 



V. Marks of Specialization. 

 As is well known, the labium is formed by the fusion of two dis- 

 tinct appendages, the second maxilUe ; and hence the most primitive 

 form would be that which showed most clearly the parts of the 

 original components. Now in this simple and primitive labium we 

 should find a submentum, a mentum, a ligula in which the outer 

 and inner laminae were still distinct, and a three-jointed palpus with 

 a well defined palpiger. 



