524 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



the second superior nervule originates from the main stem, neither its 

 basal portion nor that of the first inferior nervule showing any notice- 

 able tendency to bend abruptly and to help form the termination of the 

 cell, as now appears in all Prwfecti to a greater or less extent, and 

 which, in some open-celled genera, seems to indicate the loss of a 

 transverse discoidal veiulet after a previous possession. The presence 

 of a transversely disposed pair of spots in the costo- subcostal interspace 

 also indicates the probability that this interspace had hitherto never 

 been narrower nor bridged by a vein. 



In the hind wings, there are two features of importance, besides the 

 unusual openness of the cell, which is scarcely narrowed apically. The 

 first is the course of the first subcostal veinlet, which originates far 

 toward the base of the wing, and terminates where the costal nervureis 

 sure to end in nearly all Frcefecti,* at the upper outer angle of the wing. 

 This necessitates a shortening of the costal nervure. I do not know of 

 a single instance of such a feature among the members of this group of 

 Nynijphales, but it is an almost persistent character in the Pierids, and 

 very common in the Satyrids. The other point is the extreme narrow- 

 ness of the upper as compared with the lower median interspace, the 

 former being scarcely more than half as broad as the latter, owing to 

 the slight divergence and continual proximity of the outer branches of 

 the median vein. The only other feature in which it differs unusually 

 from its allies is in the brevity of the antennae. 



Frodryas perseplwne. — A single specimen (No. 394) was found in the 

 Tertiary strata of Florissant, Colo., by Mrs. Charlotte Hill. It is in a 

 wonderful state of preservation, the wings expanded as if in readiness 

 for the cabinet and absolutely perfect, with the exception of the tail of 

 the right hind wing. The thorax and abdomen are perfectly preserved, 

 but indications only of the legs are seen beneath the wings. The head 

 is twisted so as to throw both antennse upon one side, and to exhibit the 

 palpi better than would otherwise be the case. The tongue is doubtless 

 preserved, but the danger of injuring the palpi prevents me from chip- 

 ping the stone to find it. The autennue are nearly perfect, but the stalk 

 is covered with a thin film of stone, which will not scale, and thus con- 

 ceals the joints. The markings of the wings are perfectly preserved, 

 but on the costal area of the hind wings are partially concealed by the 

 overlapping of the front wings. In many parts of the wings, the form 

 of the scales even can be determined under the microscope. This I 

 was unable to do in any of the European fossil butterflies, although in 

 some the points where they were inserted could be seen. 



The wings are rather dark brown, deepening in tint on the front wings 

 toward the extreme base and along the immediate costal edge, orna- 

 mented with pale markings, which were, perhaps, bright-colored in life. 

 Front wings with a mesial, transverse, slightly arcuate baud, extending 



* In Polygonia aud some of its immediate allies, the upper outer angle of the hind 

 wing is curiously excised, throwing the costal nervure back some distance. 



