162 FAUNA ANTIQUA SIVALENSIS. 



fig. 4 has this peculiarity, that instead of the anterior portion of the tooth 

 being one continuous offset from the exterior line of enamel, it only 

 assumes that appearance after considerable detrition, consisting at 

 first of a short offset and an isolated pillar, as shown in the drawing. 

 The two sides of the jaw have been very unequally worn, in conse- 

 quence of which the opposite side to that delineated has the pillar and 

 offset conjoined. The third molar also presents a marked difference 

 when placed in juxtaposition with the con-esponding teeth of the 

 other three jaws : the two spurs which occupy the central hollow of 

 the tooth are of a different shape from that which occurs in the other 

 specimens. In other respects, fig. 4 corresponds with them : its rows 

 of molars are parallel to each other, and the dimensions offer but 

 trifling variations. The modifications of form above alluded to, unless 

 fortuitous, which is perhaps improbable, denote the existence of 

 another species — a fact corroborated by the examination of the milk 

 molars of the lower jaws in our possession. Upon the consideration 

 of these we now enter, but are able to offer but few and unsatisfactory 

 remarks. 



Lower Jaws. — With the exception of the fine fragment, fig. 6, PL XVI., 

 submitted to our inspection by Conductor Dawe, and the fragment, 

 fig. 9, the specimens of lower jaws are aU from the Maginnud deposit, 

 and all the remains of young animals. 



Fig. 1, PI. XVI., represents a fossil which has lost the interior of its 

 symphysis, the second molar on the right, and the first molar on the 

 left side of the jaw, as also both the rami, which are broken off. Four 

 molars have appeared, the second and third of which are worn ; but 

 the first and fourth have their enamel intact. The sections of fracture 

 expose germ teeth. The two lines of molars have a gentle conver- 

 gence, which is effected, not by a curve in the rows of teeth, for these 

 are set in a perfectly straight line, but by the gradual approach of the 

 two rows, which make a small angle with the median line of the jaw. 

 The section shown by the break of the symphysis and the interval 

 between the front molars argues the existence of a prolonged sym- 

 physis. The fourth molar is characteristic, having an isolated point 

 or low pillar in the centre of the chord of its posterior crescent. 



Fig. 4 is the right half of the lower jaw of a young rhinoceros, 

 but of one somewhat older than the animal to which fig. 1 belonged, 

 for the fourth molar has in fig. 4 suffered detrition. Notwithstanding 

 the difference of age being in the favour of this specimen, the space 

 occupied by the four molars is less than that of the four in fig. 1. 

 The fourth molar is here devoid of the low isolated pillar in the pos- 

 terior crescent, and has the central enamel, or junction of the two 

 crescents, larger than in fig. 1. There are no means of ascertaining 

 whether or not the opposite rows of molars were parallel, but in the 

 position of symphysis and set of the teeth in a perfectly straight line, 

 this specimen corresponds with the foregoing. 



Fig. 2 has its fourth molar just disclosed, and rising into the line 

 of molars. It is devoid of the isolated pillar ; but in size corresponds 

 •with fig. 1, instead of fig. 3, to which latter it assimilates itself by the 

 fourth and second molars. 



It is difficult to ascertain the degree of importance to be attached 

 to such points of difference. In no specimen from the jaw of an adult 



