116 
Psyche 
[December 
the wing. Sialis mohri Ross has been used in this study; 
the other genera of this family differ only slightly. Neoher- 
mes calif ornicus (Walker) (Corydalidae) has been used in 
the study of wing articulation, since the wing base is 
larger and apparently less specialized than in Sialis. 
Material of Lemmatophora typa examined includes the 
neotype, M. C. Z No. 3536, which is almost perfectly pre- 
served, and upon which Figures 3 and 4 are largely based. 
Of a long series of impressions of hind wings which were 
studied, M. C. Z. No. 4425 was best. In none of these fossil 
specimens were the extreme bases of MP and CuA pre- 
served. 
I should like to acknowledge the kindness of F. M. Car- 
penter, who has made available the material used in this 
study, and who, together with W. L. Brown and E. 0. Wil- 
son, has contributed many helpful suggestions. 
A. Structure of the Veins. 
In Sialis , the veins are not heavily sclerotized, most of 
them being formed as longitudinal folds in the membrane 
(Fig. 9b). As a consequence, these veins appear, viewed 
from one surface, as ridges, and from the other surface, 
as grooves. 
Since the fossil wings are molds of the upper and lower 
wing surfaces, it has been possible, by viewing under illu- 
mination nearlv parallel to the surface, to reconstruct a 
cross-section of the hind wing of Lemmatophora (Fig. 9a). 
This is similar to that of Sialis in the general structure 
of the veins, and shares with it a remarkable peculiarity: 
Explanation of Plate 13 
Figures 1, 2. Sialis mohri Ross. Anterior and posterior wings, showing 
venation and distribution of macrotrichia. Figures 3, 4. Lemmatophora 
typa Sellards. Anterior and posterior wings, showing venation and dis- 
tribution of macrotrichia. Figure 5. Pteronarcys calif ornica Newport. 
Portion of anal fan of posterior wing, showing macrotrichia on veins and 
membrane, and distribution of microtrichia. Figure 6. Sialis mohri. Struc- 
ture of microtrichia and a macrotrichium. Figure 7. Sialis mohri. Portion 
oi anterior wing, showing distribution of macrotrichia and microtrichia. 
(Microtrichia indicated by stippling.) Figure 8. Lemmatophora typa. 
Portion of anterior wing, showing distribution of macrotrichia and 
microtrichia. (Pigmentation indicated by stippling.) 
