116 U. 8. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



Platte specimens, on an average, a greater height of the zygoma anteriorly, a narrower forehead 

 between the eyes, and a rather -decided average superiority in the length and width of the 

 sectorial teeth. Still specimens may be found not exceeding, in this last respect, the Rocky 

 mountain and California specimens, and all the other characters of these are reproduced in one 

 or other of those from the Platte. 



A fact however, of some importance is, that in none of the Texas or California specimens are 

 there any with sectorial teeth so large, or with zygomata so high, as in a number of Platte 

 skulls. It is possible that, with a difference of species, two or more may be found on the 

 Platte and upper Missouri. Still these differences of condition do not admit of any assorting 

 into series, as even if several specimens agree in one point and disagree with all the rest, a new 

 combination is required if a different character be selected as the test. 



Upon the whole I am inclined to think that the differences in the skulls from the Platte are 

 due entirely to age, sex, and perhaps race. The young skull widens considerably in its lateral 

 dimensions, independently of the elevation of the median crest. The female preserves through 

 life more the characters of the young skull as to proportions. Sometimes a small skull will 

 indicate extreme age in the worn condition of the teeth, when not much more than three-fourths 

 the size of another with teeth entirely perfect. 



A very immature skull of the prairie wolf, (IIYB,) from the upper Missouri, differs materially 

 from the adult. The most striking feature is the entire absence of the post-orbital process of the 

 frontal bone, without even a slight fossa to indicate its position. It would almost seem as if 

 this were formed by the strong compression of the temporal region just behind a certain point 

 in the orbit, and under the place of attachment of the muscles of the temples. 



There is no trace of any temporal, sagittal, or occipital ridge. The dried skin of the palate 

 shows the existence of ten transverse ridges of the soft palate. 



The teeth are entirely the deciduous ones and present the following formula : Incisors, 

 ^; canines, ~ ; molars, |jj| = 28. These are, as usual, much smaller than their successors. 

 The incisors are shaped like their successors, the upper ones trilobed, the lower, bilobed ; the 

 outer upper incisors instead of having, as in the adult, no lobes at all, have a slight one on the 

 inner edge and a small spur externally, about midway to the base. The upper canines are 

 very much more curved and hooked than their successors, without sharp ridges. The lower 

 incisor is likewise shorter and more curved than its successor, and when viewed from in front, 

 exhibits a prominent angular spur on the inner anterior edge. The first upper molar is very 

 low and obtuse with a tubercle behind. The second molar is shaped like the adult sectorial 

 tooth, except that the inner spur, with its pointed tubercle, is situated opposite the base of the 

 middle lobe. There are also two additional tubercles, one at the base of the anterior trenchant 

 edge of the long pointed lobe of this tooth, and another a little in advance and exterior to it at 

 the anterior extremity of the tooth. The single tubercular molar resembles the first true or 

 tubercular permanent molar, but is much simpler. There are the two external tubercles and 

 the two which are seen nearly in the centre of the permanent tooth, but these form the exterior 

 boundary instead of being enclosed as in the adult, by a wall which, commencing on the 

 anterior wall of the tooth and passing down below the level of the anterior tubercles, comes 

 gradually up on the inner side of the tooth, and constitutes a distinct compressed tubercle on 

 the interno-posterior corner. This wall is wanting entirely in the deciduous tooth. The lower 

 temporary sectorial is quite similar to the permanent one, except that the posterior edge of the 

 middle lobe is nearly opposite to the centre of the tooth, instead of the posterior third. 



