E. H. Sellards — Types of Permian Insects. 355 



against or partly under that vein. The first anal is strongly 

 curved at the base as in the case of other genera of the family. 

 Cross veins are numerous but weak. The radius is much 

 thickened at the base. 



The special peculiarity of this genus is the late origin of the 

 media, and the close approach of the cubitus to the radius. 



Width of the wing, 4 l/2 mm ; length, partly estimated, 15 mm . 



Doter minor gen. et sp. n. Text figure 13. 



The genus Doter is proposed for a small insect the rela- 

 tionship of which has not been fully determined. The genus 

 clearly can not be referred to the Protereismephemeridse, the 

 venation being altogether different. It is possible that the 

 genus will be found to fall within the Protephemeridse. The 

 body is small and slender ; the abdomen is of equal width 

 throughout or nearly so ; the segments are short, being wider 

 than long. The abdomen is terminated by two caudal setse. 

 Two wings only are preserved on the type specimen. These 

 are proportionally large, longer than the abdomen, and of an 

 ovate shape, the inner border full and rounded. A costal 

 brace such as is seen in the Protereismephemeridae is lacking. 

 The subcosta and the radius are either united at the base or 

 lie so closely together as to give the appearance of being united. 

 The sector is three branched. The media is simple. Cubitus, 

 is three branched, cubitus 2 five branched. Two anal veins are 

 seen beyond the cubitus. The wing membrane is thin and 

 clear and the veins distinct. Cross veins occur but are not 

 numerous. 



Length of the wing, 7 mm ; width, 2 l/2 mm . 



Total length of body, (not including setse), 4 mm . 



Notwithstanding the presence of fully developed hind wings, 

 the relationship of the Protereismephemeridse is much closer 

 with the Ephemeridse than with the earlier and somewhat 

 doubtfully constituted groups of Palephemeridas and Prote- 

 phemeridae. The venation agrees essentially with that of the 

 more generalized of the modern Ephemerids. The wing is 

 similarly, although often not so strongly, corrugated. The 

 main veins are readily identified with the corresponding veins 

 in the wings of modern forms. 



The conclusions of Comstock and Needham* regarding the 

 homologies of the main veins of the wings of Plectoptera find 

 support from a study of these earliest known true Ephemerids. 

 * Amer. Nat., vol. xxxiii, p. 117, 1899. 



