RHINOCEKOS HEMITCECHUS. 331 



of a penultimate upper molar, of which the crown is but 

 slightly abraded, and the ' crochet ' well developed. In this 

 case, also, the crochet forms, at its offset, a very open angle 

 with the disc of the posterior colline. In fact, it is continued 

 in nearly the same line of diagonal as the latter, and points 

 to the anterior outer corner of the crown. Gervais (Paleon- 

 tologie Francais, PI. II. fig. 5) has given a beautiful illus- 

 tration of an upper molar (penultimate or antepenultimate) 

 of the same species, yielding precisely the same characters 

 (reproduced in PI. XVIII. fig. 4) ; and I have, through the 

 kindness of M. Gervais, had an opportunity of examining a 

 considerable number of molars of the same species in the 

 Museum of the Faculty of Sciences at Montpellier, which 

 presented a constant agreement in the offset of the crochet 

 from the posterior colline, at a small inclination only. 



If on the other hand the penultimate true molar in Rhin. 

 hemitoechus (PI. XVI. fig. 1, m. 2, and fig. 3) be examined, 

 the crochet (a) presents a thick massive body thrown straight 

 forward, and forming an acute angle with the anterior 

 margin of the posterior barrel. It is flat or concave above, 

 and convex below ; narrow at the base, and thickening to a 

 blunt margin. In mass it bears a much larger proportion to 

 the disc of the hind barrel than in most of the other species. 

 The distal extremity is closely approximated to the anterior 

 barrel, but always remains detached, undivided, and free 

 from the booked inflection, so common in the other species, 

 which suggested the name applied to this body by Cuvier. 

 The pattern presented by the stage of abrasion seen in fig. 3, 

 PL XVI., may be compared to a boot of which the disc of the 

 hind barrel forms the leg, and that of the ' crochet ' the foot. 

 In the corresponding molars of Rhin. megarhinus already 

 cited, namely fig. 5 of PI. III. of De Christol's memoir (re- 

 produced in PI. XVIII. fig. 3), and fig. 5 of PI. II. of Gervais' 

 Paleontologie (reproduced in PL XVIII. fig. 4), besides the 

 difference of alignment in its offset from the hind barrel, the 

 section of the crochet is wedge-shaped, thinning from a broad 

 base to a sharp edge. 



In the antepenultimate true molar, m. 1 of fig. 1 of PL 

 XVI., the same general characters are presented, but modified 

 by the greater age and more advanced abrasion of the crown. 

 The posterior valley is reduced to an oval pit. The discs of 

 the anterior and posterior barrels occupy much larger areas ; 

 the crochet being ground low down is greatly diminished in 

 projection, but it still forms a right angle with the anterior 

 edge of the posterior barrel. The cul de sac of the middle 

 valley is reduced in size, and a ' combing plate ' or fold of 

 enamel from the outer longitudinal ridge juts into it, directed 



