234 MK. R. I. POCOCK ON THE 



nearly straight when viewed from above or below, but with the 

 upper margin concave, the lower convex. The slightly raised 

 distal expansion, hollowed above like a shovel, is irregularly semi- 

 circular in shape, and has a continuous unevenly denticulated 

 edge, without median notch ; and the apex of the shaft of the 

 baculum projects forwards as a process from its lower surface. 

 The bone measures about 3 mm., and the width of the distal ex- 

 pansion is about half the length of the shaft. (Text-fig. 26, A, B.) 



The baculum of a specimen of C. leursi from Jalisco, in 

 Mexico, has the shaft very broad at the base, whence it gradually 

 naiTOws to the expansion. Its upper and lower edges are nearly 

 straight from the lateral view, but from the dorsal view the shaft 

 is seen to bend distally slightly towards the right. The disc is 

 relatively and actually much wider than in C. mongolicus, and 

 its right side is produced more than the left ; but its edge is 

 continuous, without median notch and more regularly denti- 

 culated than in C. mongolicus. There is, moreover, no process 

 representing the tip of the shaft on the under side of the disc. 

 The bone measures 5 mm., and the width of the disc is almost 

 equal to the length of the shaft. (Text-fig. 26, C, D.) 



In two examples of C. mexicamus, one from the City of INIexico, 

 the shaft difi'ers from that of C. mongolicus and leursi in having 

 its upper edge abruptly inclined downwards and distally towards 

 the disc ; and the disc itself difters in having a deep median 

 notch in its margin and in being much more strongly bent 

 upwards, so that its hollow is much deeper and more triangular 

 in shape. As in C. mongolicus, the apex of the shaft is con- 

 tinued as a short process projecting from the lower surface of 

 the disc in front a little beneath the notch. The bone measures 

 about 5"5 mm. and the greatest width of the disc across its 

 posterior angles is less than half the length of the shaft. 

 (Text-fig. 26."E, F.) ' 



In a specimen of C. \?>-lineaius from Minnesofcx the shaft is 

 intermediate in shape between that of C. mexicanus and of 

 C. leursi; but the disc difi'ers from that of the other sj^ecies in 

 having its edge broad and furnished with two rows of teeth. It 

 is, moreover, very definitely divided into a right and left lamina 

 by a wide and moderately deep median notch in front, and it ia 

 somewhat abriiptly upturned. The tip of the shaft shows as a 

 low, indistinctly defined rounded boss on the under side of the 

 disc just below the notch. The bone measures 5 mm. and the 

 width of the disc is about half the lencjth of the shaft. (Text- 

 fig. 26, G-I.) 



a. Edge of tlie apically widely notched disc liroad and aniicd witli two 



rows of teeth lo-Jiiieati($. 



a'. Edge of the disc narrow and armed with" a single row of teeth. 

 b. Disc nearly vertically riptnmed, with a narrow median notch in 



front: nxi;-er surface of shaft distally geniculate mexicanus. 



b' Disc a little upturned, without median notch: shaft not distally 

 geniculate above. 



