1 96 Bulletin American Museum of Natural History. [Vol. XXII, 



3 . Tatu novemcinctum mexicanum (Peters) . 



Twenty specimens, all from the immediate vicinity of Escuinapa, 

 Dec. 28-Jan. 7, and one each Feb. 9 and March 5. Only 4 have fully 

 acquired the permanent dentition, and only one has merely the 

 milk dentition; in all the others the milk dentition is being replaced 

 by the permanent teeth, every stage of the change being represented 

 in different specimens. 



As is well known, the change occurs relatively late in life, nearly 

 all the specimens in the present series which show the change having 

 nearly or quite attained adult size. The sexes are about equally 

 represented. 



The females are considerably smaller than the males, as shown 

 by the following measurements: 



Eight males: Total length, 825 (744-903); head and body, 431 

 (386-483); tail, 381 (356-419); hind foot (with claws, from skin), 83 

 (80-85); ear > 37 (3 2 -4o). 



Seven females: Total length, 728 (679-762); head and body, 367 

 (330-419) ; tail, 361(330-394); hind foot (from dry skin), 82 (75-86); 

 ear, 35.4 (32-38). 



Unfortunately the front border of the nasals is defective in 

 most of the skulls, but in 4 complete male skulls the total length 

 of the skull ranges from 91-101.5, averaging 97.4; two female skulls 

 have a total length, respectively, of 85 and 89. Zygomatic breadth, 

 8 males, 38.5 (36-42); 6 females, 37.5 (35-40). Mastoid breadth, 

 8 males, 27.5 (26-28.5); 6 females, 26.5 (25.5-27). 



The number of teeth varies from f if to fif , as follows: 5 skulls, 

 JlJ; ii skulls, -fif; 2 skulls, fif; i skull, z|; i skull, fif. The 

 skull varies greatly in different specimens independently of sex or 

 age, particularly in the relative length and breadth of the rostrum, 

 and in other individual elements, as notably the lachrymal bone. 

 The nasals vary in width (at the narrowest part) from 4.5 to 7 mm., 

 and also vary in relative length. The lachrymal varies greatly in 

 size, and also in form, from triangular to quadrate. Generally it 

 is triangular, with the apex forming a sharp angle at the antero- 

 superior border, the upper border being straight and horizontal, 

 and the anterior border a straight obliquely descending line ; the lower 

 border and also the posterior border are sometimes approximately 

 straight, although the former more commonly rounds upward to meet 

 the front border without forming a distinct angle. The lachrymal is 

 thus usually three-sided, with the upper and posterior margins straight 



