1889.] NATURAL SCIENCES OF PHILADELPHIA. 339 



In Vesperus fuscus (No. 5973 S. I.) the postdigital nerve of the 

 fourth interspace was the same as in Vespertilio. This was the 

 only example of important variation which I noted in this common 

 species. 



In one example of Mormoops blainvillei a supplemental line 

 appeared on the right side between the intercosto-humeral and the 

 internal-cutaneous systems. 



The most constant disposition of nerves was seen in the third 

 interspace, and defined the greatest number of groups. The limi- 

 tation of smaller groups and the place of most decided variation 

 was in the region of the fifth metacarpal bone. The fifth digit was 

 more highly endowed with muscle — indeed was the only digit 

 which exhibited a well-defined muscle-mass at the proximal end. 

 The varying ami important raised folds here took their origin, as 

 well as special lines which extended along portions of the entire axis 

 of the digit. The dispositions of some of the interdermal lines in 

 the mesopatagium bordering the digit, especially at and near the 

 radiometa carpal angle, were so variable, that no attempt was made 

 to describe them. It becomes of interest, therefore, to compare this 

 region of the greatest variability with that of the region of the least 

 variability, — the third interspace, — and infer from such data some- 

 thing of the movements of the several parts of the manus in the 

 living individual. The fifth digit would appear to determine more 

 changes, or at least be associated with more changes, than any other 

 portion. 



The general arrangement of all parts was much the same in 

 groups already well defined. Thus the Pteropidae, Nyeteridse, 

 Vespertilioiiiihe, PhyllostomidaB, etc., each had a distinctive plan. 

 In the group last named all the true leaf-nosed forms agreed in 

 having a longitudinal line in the middle of either the fourth or the 

 third interspaces or in both. The absence of the line in Mormoops 

 is suggestive of the false position of this genus in this group, while 

 the general harmony of the details with those of the Emballonourida? 

 gives ns the hint as to what the true position may be. In the genus 

 Miniopteris a similar suggestion can be made. Natalus and 

 TJujroptera already known to be isolated forms remain so from the 

 evidence yielded by the membranes. Thyroptera appears to be a 

 highly specialized aberrant Vespertilionid. 1 



1 I have reserved for a separate use descriptions ot the markings on lhe wings 

 of Molossi. They differ from those of other groups and are distinctive. The 

 pannicular system here attains the highest development. 



