MUSEUM OF COMPARATIVE ZOOLOGY. 277 



Gerephemera simplex. 



I have not seen the type, but only the unfiguii'tl and undescribecl reverse of a 

 small portion, belonging to the Boston Society of Natural Historj'. Therefore 

 my opinion is bused chiefly upon Fig. 8 and the very detailed description. 

 The description differs from the figure (of natural size) in the statement (p. 13) 

 that " the niei-est fragment of the costal border 2 to 3 mm. long is preserved," 

 uhereas the figure has it 8 mm. long, with two oblique cross veins and indications 

 of quadrangular cells between them. As these cells are not mentioned in the 

 description, they were perhaps not present in the specimen. These cells would 

 be of prominent importance if they were really situated near the costal border. 

 But it is not uncommon to find in badly preserved fossil wings some parts folded 

 up and appearing in the wrong place. If they are j^resent as figured, they 

 could be explained in another manner, which will be quoted hereafter. The 

 specimen is unfortunately not on a level, but upon a somewhat rounded ground- 

 floor, and shows a kind of sulcus, which certainly does not belong to the wing. 

 Therefore all parts of the wing situated in the sulcus are not quite in a natural 

 position. The statement of the author (p. 14), "that the mediastinal vein is 

 never a depressed one in such insects," should have been just the contrary. 



The fragment represents a diagonal part of the middle of the wing of a 

 dragonfly. What is called "the uppermost vein of the lower set" is probably 

 the sector medius, and the vein running a little beloAV in the same direction is 

 the sector brevis. All the parallel veins above those sectors, which give so much 

 trouble to the author, are easily to be accounted for in the venation of the 

 Odonata. The fragment is very rudimentary, and it seems by no means cer- 

 tain that the two veins indicated on the tip (if figured in the right place) be- 

 long to the marginal veins. Perhaps they may belong to the sector nodalis 

 and sub-nodalis. The determination of Fig. 8 cannot go farther than to state 

 that the specimen belongs to the Odonata and to a very large species. All im- 

 portant characters for the determination of the genus, and even of the sub- 

 family, are to be found in parts of the wing which are not here preserved. It 

 seems, to judge from the veins which are visible, that the small part called the 

 front margin was situated behind the nodus. Species are known with an irreg- 

 ular venation just behind the nodus, but not of a similar irregularity. Con- 

 sidering the other characters agreeing with the Odonata, this peculiar feature 

 would not indeed warrant us in excluding this species from this family. But 

 it is more probable that the small part does not belong to the front margin, and 

 similar cells are likewise found in Isophlebia. 



The new family Atocina, created by the author for this specimen, and the 

 whole discussion about it, cannot be accepted as it is. In his first letter, in 

 1865, the author states that " this species borrows some striking points of the 

 peculiar wing-structure of the Odonata, and combines with them those of fam- 

 ilies remote from that, and even >>elonging to a distinct section of the Xeurop- 

 tera, exhibiting to our view a synthetic type combining the Pseudoneuroptera 

 and the Neuroptera. I am unable to find in the figure and in the new 



