366 



rigs. 1-6.- 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[June 4, 

 and Hypsiprymnus 



-Tlagiaulax Becklesii (figs. 1-5), 

 Gaimardi (fig. 6). 

 Pigs. 1 & 4 show the entire Right Bamus of the Lower Jaw o/Plagi- 

 aiilax Becklesii, in two pieces, on reversed slabs of the same piece of 

 matrix. (Magnified two diameters.) 



2. 3. 



J. 3 



[Figs. 1 & 4 represent the same right ramus of the lower jaw seen on the 

 opposite surfaces of a split stone, the two taken together affording data for a 

 complete restoration of the jaw.] 



Fig. 1. ab e'. Outer side of the anterior portion of the right 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 premolars. 



d'. Impression in the matrix of the condyle. 



e'. Impression of top of coronoid process. 



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



m. Place of the two molars. 



pm. Three premolars, the third or last divided by a crack. 

 Fig. 2. /. Section of the anterior piece of the jaw at the fracture h c ; x, in- 

 ner surface ; y, outer. The notch at the top is formed by one of the 

 sockets of the double-fanged true molar. 

 Fig. 3. g. Section of the hinder piece near be, x, inner surface ; y, outer 



surface. 

 Fig. 4. a' d. Inner side of the posterior portion of the same lower jaw on 

 the opposite slab of stone ; b d e^ inner side ; ba' h, cast and im- 

 pression of outer side. 



a'. Outline of the incisor restored. 



b c. Line of vertical fracture. 



d. Condyle. 



e. Coronoid pa'ocess. 



h. Impression of the three premolars on the matrix. 

 i. Empty sockets of the two true mo^.ars. 

 n. Orifice of dentary canal. 



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

 Fig. 5. Jc. Tliird or largest premolar, showing the seven diagonal grooves ; 



magnified 5^ diameters. 

 Fig. 6. I. Corresponding premolar in the recent Australian Hypsiprymmis 

 Gaimardi, showing the seven vertical grooves ; magnified 3^ diameters. 



