PURBECK FORMATIONS. 55 



root of the zygoma may include the antorbital foramen (/). The outer wall of the upper 

 jaw in advance of this is remarkable for its height and verticality, and for the arched 

 convexity which defines it above, the thick or broad hind part of which arch may be due 

 in part to a nasal bone combined with the maxillary. A crack, fissure, or sutural ' har- 

 monia' runs from the interspace between the second and third teeth in place some way 

 upward where all trace of it is lost. The determination of the teeth depends on the 

 demonstration of the character of this fissure which the present material does not afford. 

 If it be a suture the two anterior teeth are in the premaxillary; if it be an accidental crack, 

 the premaxillary may be wanting at the fore part of the specimen and the foremost tooth 

 would be a canine. Under this doubt I shall merely indicate the six teeth in place, as 

 they follow from before backward, by consecutive numerals, although the last four with 

 complex crowns are 'molars,' by the character of shape. 



The laniariform tooth (1), if a canine, is unusually large among the small Purbeck 

 Mammals : the crown is robust, and terminates somewhat obtusely, retaining its thickness 

 nearer to the apex than usual ; in section it is a very full oval, much less compressed than 

 in the canines of any other Mesozoic Mammal. The inner side is less convex across than 

 the outer. The enamel there shows two or three low linear longitudinal risings. There 

 is an indication of a rugous talon behind the base of the crown. This tooth is implanted 

 by a single thick root. 



The succeeding tooth (2) is of much less size ; it is also implanted by one large root, 

 which expands into a low stumpy bulging crown, consisting of one chief thick cone, with a 

 small anterior and posterior ridge-shaped cusp. The enamel is rugous ; it swells out 

 beyond the smooth fang to form the base of the crown, without, however, defining a distinct 

 cingulum. This tooth is contiguous to No. 1. 



An interval of the breadth of the tooth (2) divides it from the next (3) ; the alveolar 

 part of the jaw is there broken, or seems so, if the fissure be not sutural. The outer side 

 of the crown of the tooth (2) developes a low thick stumpy cone {a) -. the inner side divides 

 into two similar cones. The outer cone {a) is the largest, the antero-internal one {b) the 

 smallest, but the difference is slight. Of the two inner cones or tubercles, one is rather 

 in advance of the outer cone, the other is on the same transverse line therewith. The 

 enamel forming the low apex of each cusp or cone is rugous ; it is smooth and polished 

 where it covers the outer bulging convex base of the crown. The rugosity is due to ridges 

 converging toward the apex. 



The next tooth (*) in close contiguity with the last is of similar size and shape ; but 

 the antero-internal cusp {b) is rather larger. In both teeth a low ridge passes from the 

 back part of the base of the external cusp («) to that of the post-internal cusp (c) connecting 

 them. The succeeding tooth {s) seems not quite to have ' come into place.' The external 

 cusp is below the level of that of the antecedent tooth, and so are the just visible apices of 

 the two internal cusps ; it evidently has a crown of like size and character with that of the 

 foregoing teeth; but fracture interferes with a satisfactory appreciation of the modifications 



