﻿MYOTIS THYSANODES. 



83 



Central lower incisors with crowns compressed and trifid, the next 

 pair similar but larger, the outer incisors still larger and with crowns 

 indistinctly terete and quadritubercnlate. First and second mandibu- 

 lar premolars variable in position and in relative size, the first always 

 the larger. The second is shorter than the first, but in some specimens 

 its crown has a cross section nearly equal to that of the latter. The 

 first is always in contact with the canine and usually with the second 

 premolar also, but may be separated from the latter by a narrow space. 

 The second premolar is either wholly in the line of the tooth row and 

 not touching the third, in line and touching the latter, or more or less 

 displaced inward. Third premolar trapeziform, slightly broader than 

 long. 



In dentition Myotis thysanodes shows many points of difference from 

 M. velifer. One of the most striking of these is the great variability 

 in the size and position of the first and second upper premolars (figs. 

 16 and 17), which in M. velifer are comparatively constant. Other dif- 

 ferences may be seen in the form of the third upper and third lower 

 premolars. The crowns of the upjjer molars are proportionally broader 

 in 71/. velifer than in M. thysanodes. 



Measurements. — Average measurements of 23 specimens of Myotis 

 thysanodes from four localities are given in the following table : 



Average measurements of 23 specimens of Myoiis thysanodes from 4 localities. 



Locality. 



Number of 

 specimens. 



Total length. 



S 

 += 



% 

 H 



Tibia. 



Foot. 



Forearm. 



Thumb. 



Longest fin- 

 ger. 



Ear from mea- 

 tus. 



Width of ear. 



Tragus. 



California: Old Fort Tejon 



If 



87 



36 



18 



8 



41 



6 



69 



18 



12 



11 



Old Fort TeJon 



10 



87 



37 



17.6 



8 



41.2 



6.3 



69.2 



17.6 



11.8 



10.5 



Michoacan : Patzcuaro 



3 



89 



37 



16.7 



8.9 



41.8 



6.7 



71.5 



18.3 



n.9 



10.8 



San LuisPotosi : Hda.LaParada 



10 



90.4 



36.9 



17.4 



8.9 



42.7 



6.7 



73.6 



18.5 



12.2 



10.5 



' Type. 



Specimens examined. — Total number 88, from the foUowiug localities : 



California: Dulziira, 1 (skin, Miller coll.) ; Old Fort Tejon, 16. 

 Chiliualiua: East side San Luis Mountains, 2 (skins). 

 San Luis Potosi : Hacienda La Parada, 62 (6 skins). 

 Michoacan: Patzcuaro, 5 (2 skins). 



Jalisco : LaLaguna, Sierra de Juauacatlan, 1 (skin) ; Sierra Nevada de Colima, 

 1 (skin, Am. Mus. Nat. Hist.) . 



General remarhs. — Myotis thysanodes needs no close comparison with 

 any other species occurring in Mexico or the United States. Its large 

 size separates it from all others but M. velifer, while from the latter the 

 ciliated free border of the uropatagium, peculiar thickened calcar, 

 larger ears and paler color together with the cranial and dental 

 characters readily distinguish it. 



