CARBONIFEROUS ARTHROPOD FAUNA 1 97 



One specimen, represented by the obverse and its reverse. 

 Mazon creek, 111., Carboniferous. From the Egan collection of 

 the Chicago Academy of Sciences, No. 4749. 



This is by far the best specimen of the ironstone fossils, the 

 insect being preserved with the wings of the right side extended 

 and not overlapping; the neuration is perfect. 



Inasmuch as Dr. Scudder states that the figure of Chrestotes 

 lapidea is erroneous in part, and elsewhere characterizes the genus 

 as having the scapular vein and its main branch approximated, we 

 shall have to regard the present specimen as excluded from this 

 genus. With Hemeristia it therefore agrees in this character, 

 and in the disposition of the main veins, but here the veins are 

 straight and simply connected by transverse cross-veins, and 

 exhibit no trace of reticulation. Thus the present genus is 

 characterized briefly by the angular course of the veins and the 

 prominent reticulation of the cross-veins. 



Family Gerarina Scudder. 

 22. Gerarus danae Scudder. 

 Geol. Surv. III., Vol. Ill, p. 566, Fig. i. 



There is in the university collection what we have reason to 

 believe is the type of this species, inasmuch as the strange out- 

 line of the body together with the general neuration is as 

 depicted in the figure. However, the shape of the rather large 

 and rounded stone is quite different from that in Dr. Scudder's 

 illustrations. Should this be the type, a slight error has been 

 committed in figuring the termination of the mediastical vein. 

 Toward the tip, this becomes irregular, owing to its flexture at 

 each cross-vein. This might lead one, especially in a poorly 

 preserved specimen, to suppose that the mediastinal terminates 

 in the scapular vein, or, as in Xeno?ieura antiquoriim Scudder or 

 Dictyoneura libelluloides Gold., that it ends in a cross-vein rec- 

 tangularly bent, its upper half somewhat the longer. However, 

 in such a case the great length of the mediastinal vein, together 

 with the numerous under-branches of the scapular, would easily 

 lead one to recognize its affinities with this family. 



Type. Pal. Coll. No. 9245, 



In addition to the twenty-three species here enumerated there 



