98 PROCEEDINGS OF THE NATIONAL MUSEUM vol. no 



ley, H. B. Hitchcock, Patricia Isham, E. V. Komarek, Barbara 

 Lawrence, R. E. Mumford, Thelma Reid, C. C. Sanborn, William 

 Schaldach, Jr., Albert Schwartz, P. M. Smith, P. W. Smith, Ai-thur 

 Stupka, Robert Traub, Bernardo Villa R., and F. N. Young. 



I am thankful to the persons who reviewed the manuscript and 

 offered helpful criticism and advice: A. M. Elliott, C. W. Hibbard, 

 E. T. Hooper, Remington Kellogg, D. H. Johnson, H. W. Setzer, 

 A. H. Smith, and C. F. Walker. 



Methods 



In tables 7-18 cranial and external measurements, in millimeters, 

 are given for Euderma maculatum, Plecotus auritus, Plecofus phyllotis, 

 and for all the races of the subgenus Corynorhinus. Females are 

 significantly larger than males in these bats. Accordingly, measure- 

 ments for the two sexes are tabulated separately. Only adults, as 

 determined by ossification of the linger joints and appearance of the 

 skull, were measured. 



Measurements of Euderma are from the following sources : Ashcraft 

 (1932, p. 162), Durrant (1952, pp. 59, 66), Nicholson (1950, p. 197), 

 Parker (1952, p. 480), Stager (1957, p. 260), and four specimens 

 measured by me. 



External measiu-ements of Plecotus, except of the forearm, are those 

 taken by the collectors. I measured the forearm (greatest length of 

 radius-ulna including carpals) on the preserved specimens . All cranial 

 measurements (fig. 1) were taken with dial calipers and the aid of a 

 binocular microscope in the following manner : 



Greatest length: Distance, on the diagonal, from the anteriormost border of the 



premaxilla to the posterior limit of the supraoccipital; incisors are excluded. 

 Zygomatic breadth: Greatest distance between the outer borders of the zygomatic 



arches. 

 Interorbital breadth: Least diameter of the interorbital constriction of the 



front als. 

 Brain case breadth: Distance, measured above the auditory bullae, between the 



lateral limits of the parietals. 

 Brain case depth: Distance between the dorsal extreme of the skull and the 



ventral limit of the occipitosphenoid plate; auditory bullae are excluded. One 



bar of the caMpers lies flat on the occipitosphenoid plate; the other is in 



contact with the top of the brain case. 

 Maxillary tooth row: Distance between the anterior edge of the canine and the 



posterior border of the third molar. 

 Postpalatal length: Distance from the anterior limit of the mesopterygoid fossa 



to the ventral lip of the foramen magnum. 

 Palatal breadth : Distance between the lateral extremes of M ^. 



Presence or absence of a secondary cusp in I ^ was indexed according 

 to the following scale (fig. 2) : 



