THE FAMILIES AND GBNEKA OF BATS. 31 



nearly straight, though usually marked by three projections and two 

 indentations. The anterior border is unsymmetrically convex, the 

 inner border variously truncate, rounded, or double convex, the 

 posterior border with a concavity usually somewhat greater than con- 

 vexity of anterior border. The inner posterior portion of the crown, 

 bearing no large cusp, is usually flattened and often produced into a 

 noticeable heel. The crown bears three main cusps, corresponding to 

 those of the primitive tritubercular tooth, the inner anterior proto- 

 cone (fig. 4, pre), the outer anterior paracone (fig. 4, pc), and the 

 outer posterior metacone (fig. 4, roc). Not infrequently the "inner 

 posterior hypocone (fig. 4, he.) is also present, but in bats this cusp 

 never attains a size sufficient to obscure the tritubercular aspect of the 

 crown. Very rarely (in some Phyllostomidse, particularly Brachy- 

 phylla, Plate VI, fig. 3) an intermediate cusp, the protoconule, occurs 

 between protocone and paracone, and another, the metaconule, at 

 inner base of metacone. At the extreme outer edge of the tooth are 

 three small cusps, the anterior parastyle (fig. 4, ps.), the median 

 mesostyle (fig. 4, ms.), and the posterior metastyle (fig. 4, mts.) a . 

 The styles are connected with the main cusps of the outer row by four 

 conspicuous, trenchant, slightly concave ridges, or flu tings, the com- 

 missures (fig. 4), the first extending from parastyle to paracone, 

 the second from paracone to mesostyle, the third from mesostyle to 

 metacone, the fourth from metacone to metastyle. The commissures 

 are approximately equal in length, though increasing slightly from 

 first to fourth. Together with the cusps, which they connect, these 

 ridges form a conspicuous W-pattern, the variations in the form of 

 which are of much systematic importance. Of the three main cusps 

 the protocone is situated at a lower level than the others. In form it 

 is more robust, though usually less elevated; frequently it occupies 

 nearly the entire inner section of the tooth. A narrow commissure 

 extends forward from anterior side of this cusp, past base of para- 



» In describing the molar teeth I have adopted the cusp nomenclature pro- 

 posed by Osborn (See American Naturalist, XXII, p. 1072, December, 1888) 

 as the most simple and convenient. The fact that it was based on a mistaken 

 idea of the succession of cusps (See Gidley, Proc. Washington Acad. Sci., VIII, 

 p. 106, July 10, 1906) is of little weight compared with the convenience of an 

 exact name for each part of each tooth. The system of numbering the cusps 

 (cusp No. l=ps, No. 2=ms, No. 3=m£s, No. 4=pc, No. 5=otc, No. 6=pc, No. 

 7=ftc, etc.) proposed by Winge (Vidensk. Meddel. Naturhist. Foren., Ki0ben- 

 havn, 1882, pp. 15-19, pi. in) and recently adopted by Andersen and Wroughton 

 (Ann. Mag. Nat. Hist, 7th ser., XIX, p. 129, February, 1907) appears to be equal!/ 

 misleading as regards the succession of cusps, while it has the great disad 

 vantage of furnishing no convenient names. With regard to the position of the 

 primitive cusp: Winge placed It in the outer row (mesostyle), Osborn in the 

 inner row (protocone), while the observations of Gidley, based on much more 

 extensive material, shows almost conclusively that it is in the middle row 

 (paracone). 



