Ch. XX.] 



MAM1IALIA OF MIDDLE PURBECK. 



383 



smaller fossil (P. 



minor, 



fig. 374), having only half the linear dimen- 



sions of the other, was probably only 1-1 2th of its bulk. It is of 



Plagiaulax BeeTclesiU Falconer. 



These two figures represent the same right ramus of the lower jaw seen on the opposite sur- 

 faces of a split stone, the two taken together affording data for a complete restoration of the 

 jaw. 



Upper figure [outer side). 



c, 5, e'. Eight ramus of lower jaw magnified two diameters, a, b. Outer side, b, o', d, e'. Im- 

 pression of inner side.- 

 ■a. Incisor. 

 b, c. Line of vertical fracture behind the pre-molars. 

 d'. Impression of the condyle in the matrix. 

 e'. Impression of top of coronoid process. 



/. Section of the anterior piece of the jaw at the fracture b, c. — x, inner surface ; y, outer. 

 The notch at the top is formed by one of the sockets of the double-fanged true 

 molar. 

 g. Section of the hinder piece near &, c ; cc, inner ; y, outer surface. 

 o'. Broken-off inflected fold of inner margin buried in the matrix. 

 m. Sockets of two molars. 

 p, m. Three pre-molars, the third and last divided by a crack. 



Lower figure {inner side). 

 of, d. Same lower jaw on the opposite slab of stone ; b, c7, 



e, inner side ; b, a\ h. cast and 



impression of outer side. 

 a f . Outline of the incisor restored. 

 b, c. Line of vertical fracture. 



d. Condyle. 



e. Coronoid. 



h. Impression on the matrix of the three pre-molars. 

 i. Empty sockets of the two true molars. 

 n. Orifice of dentary canal. 



0. Indication of the raised and inflected fold of the posterior inner margin. 



k. Third or largest pre-molar, magnified 5^ diameters, showing the T diagonal grooves. 



1. Corresponding pre-molar in the recent Australian Hypsiprymnus Gaimardi, showing 



the 7 vertical grooves, magnified 3£ diameters. 



peculiar geological interest, because, as shown by Dr. Falconer, its 

 two back molars bear a decided resemblance to those of the Triassic 

 Microlestes (&, c, fig. 375), the most ancient of known mammalia^, of 



