54 FOSSIL MAMMALIA OF THE 



main cone are well marked. Four teeth of like type precede the above premolar ; they 

 decrease in size, especially in basal fore-and-aft extent as they advance in position ; but 

 this decrease is most marked in the foremost. Each is implanted by two roots. 



From the size of the socket the antero-posterior diameter of the canine must have 

 exceeded that of the largest molar ; its crown was probably of the usual proportional 

 length. The incisors, which appear not to have exceeded three in number, were minute ; 

 they were close-set, and not divided by an interspace from the canine. All the other teeth 

 stand a little apart, as in Spalacofherium and Chri/socJdoris. The intervals are certainly 

 wider than in Stylodon pusillus. 



The outer side of this minute slender jaw is unusually convex vertically. There are 

 two anterior dental foramina, one (_/') beneath the fourth, another (/) beneath the first, 

 premolar. 



If other discoveries should better demonstrate a generic type of teeth in a mandible 

 with horizontal rami of the form and proportions here exhibited, perhaps the name Lepto- 

 cladus" might be accepted for the genus here indicated. For the convenience of registra- 

 tion I have marked the fossil as Leptocladus duhius. 



§ XIII. Genus — Bolouon," Oioen. 



This genus is founded on characters of the maxillary teeth, as shown in two specimens 

 (PI. Ill, figs. 5 and G). 



Seeing the rarity of an upper jaw as compared with a lower jaw in the mammalian 

 fossils from Mesozoic beds, one is disposed strongly to surmise that some of the many 

 mandibles in the present series must belong to the same species or genus which has left 

 the specimens about to be described. 



But there are, amongst the few examples of upper jaw, maxillary teeth with patterns 

 of crown which do permit their association with previously recognised mandibular teeth, 

 as, for example, those of Pernlestes, Stylodon, Triconodon. 



I find, however, no mandibular ramus with teeth which exemplify the same kind or 

 degree of conformity with the three remarkable ones, which have suggested the generic 

 name signifying ' lump-tooth ;' and I have, therefore, no alternative but to describe them 

 as indicative of the genus and species, described in the present section. 



Species 1. — Bolodon crassiuens, Ow. Plate III, figs. 5, 5 a, 5 b. 



In PI. Ill, fig. 5 represents, of the natural size, and figs. 5, a and b, magnified 3 diam., 

 the right maxillary, with the outer side exposed, showing the beginning of the zygoma (2), 

 and part of the lower rim of the orbit (0). A fossa anterior to the maxillary process or 



' Xeirrot, slender; i:\a6os, ramus. 

 2 (iiiXus, lump ; ohui/s, tootb. 



