1896.] ^^^ [Farr. 



is well developed on the antero-external lobe of Ds. 3 and 4, even better 

 than on the corresponding permanent tooth. It has lately been called 

 to my attention that the cingnlum varies in the individual with the 

 nourishment, well-nourished individuals having it better developed than 

 those poorly nourished, but the recurrence in many individuals of the 

 character as given above precludes the possibility of its being an indi- 

 vidual variation. The antero-internal cusp is wider antero-posteriorly 

 in the temporary teeth than in the permanent set and the bifid character 

 of this cusp is more marked in the former. All the lower milk teeth are 

 narrower and longer antero-posteriorly than the permanent teeth. Both 

 the upper and lower molars of the deciduous set are of not nearly so 

 great vertical length as those of the later series. 



The Upper Molars. 



Premolars 2, 3 and 4 are molariform and Pm. 2 is beginning to assume 

 the elongate character which is so much emphasized in the living horse. 

 The six molars (i. e., molars and molariform premolars) are nearly alike 

 in size and form. "They have square crowns, wider transversely than 

 broad antero-posteriorly and both these measurements greatly exceed 

 the length. The crowns consist of three pairs of lobes — an outer and 

 an inner pair of principal lobes and a much smaller pair situated 

 between them, the secondary or accessory lobes. The outer lobes are 

 demi-conoidal and form at their junction a narrow buttress externally. 

 A stronger buttress bounds the fore part of the anterior of the two 

 lobes. A tendency to the development of a buttress is seen also at the 

 back part of the posterior of these lobes. The buttresses expand and 

 are conjoined at the bottom of the crown, forming together a pair of 

 arches bounding the external surfaces of the outer lobes. These sur- 

 taces are nearly flat and are divided by a conspicuous median ridge. 

 The inner surfaces of the outer lobes are prominently or almost angu- 

 larly convex. The inner lobes of the crown are simply conical, wider 

 ti'ansversely than fore and aft and with the anterior slightly larger than 

 the posterior. The median lobes are not more than half the size of the 

 principal ones and appear as prominent folds curving outwardlj'^ from 

 the inner lobes to the anterior face of the outer lobes. Elements of a 

 basal ridge exist at the fore and aft parts of the crown and at the outlet 

 of the valley separating the inner lobes. In the interval posteriorly 

 between the back inner and outer lobes there exists a tubercle which in 

 association with the contiguous portions of the basal ridge assumes the 

 dignity of a sublobe." In Pm. 1 the anterior buttress is more distinct 

 or separate than in the other molars, though it is not so large. The 

 anterior of the median cusps is larger than the posterior, except in Pm. 2, 

 which is peculiar in this as in so many other respects. 



The teeth of the temporary set present the following differences from 

 those of the permanent set described above : 



1. The cusp situated between the outer and inner posterior lobes, the 



