PURBECK FORMATIONS. 45 



§ XII. GetiNs— SiYhomji, Owen, IS6G} Plate II, figs. 14— 19 ; Plate III, figs. 1—4. 



The present genus of Mesozoic Mammal was founded on a portion of lower jaw 

 with teeth (PL II, fig. 15, nat. size, 15 a, magn. five diam.) submitted to the Author 

 by his friend the Rev. Peter B. Brodie, M.A., F.G.S., by whom it had been obtained 

 from the same locality and marly member of the Purbeck beds as that which became 

 subsequently the scene of Mr. Beckles's explorations. 



The results of the latter abundantly confirm the title of this, at one time, unique 

 specimen, to the generic distinction assigned to it, and the later acquisitions instructively 

 add to our knowledge of the dental and mandibular characters of Stylodon. 



Species — Stylodon pusillus, Owen."- Plate II, figs. 15, 15 a, to 19, 19 a. 



I may be permitted to quote part of my original account of the type-specimen of the 

 present species before proceeding to the description of those discovered by Mr. Beckles. 



" The part of the lower jaw is imbedded in a small block of the matrix, with the 

 outer surface exposed : it includes the portion of the ascending ramus supporting the 

 coronoid process (a film of which only remains in the depression of the matrix, mainly 

 indicating its size and shape), and so much of the horizontal ramus as includes the alveoli 

 of the nine posterior teeth, eight of which are in sittt. The articular and .angular 

 processes, and the fore part of the ramus, have been broken away, and there is no indica- 

 tion, in the matrix, of the entire ramus having been imbedded therein ; it may be inferred, 

 therefore, that the mutilation took place prior to imbedding. Enough, however, has been 

 preserved to demonstrate the class-characters of the animal to which the fossil belonged, 

 and to enable us to add another genus and species to the small category of Mammalia of 

 the Mesozoic period. 



" The continuous unity of bone at the part of the mandible which would show most 

 of the sutures in a lacertian jaw — the height, breadth and contour of the 'processt/s 

 coronoideus ' — and the implantation of one at least of the teeth by two fangs in a double 

 socket, concur in testifying to the warm-blooded, air-breathing, viviparous, and lactiferous 

 class of the animal. The base of the coronoid process shows the raised boundary of the 

 lower part of the depression for the insertion of a temporal muscle of mammalian propor- 

 tions. The lower margin of the ascending ramus has a degree of thickness and flatness 

 suggestive of Marsupial affinities ; but the angle itself is broken off. As, however, the 

 alternative is the almost equally low ' lissencephalous ' sub-class, to which the present 

 little Insectivore must be referred, if it be not ' lyencephalous,' it adds another to the 

 prevalent testimony of the low condition of the Mesozoic mammalian life. 



' arvXof, pillar ; obovs, tooth. The ' Geological Magazine, or Monthly Journal of Geology,' &c. 

 No. xxiii, May, 1866, vol. iii, p. 199, pi. x. figs. 1 and 2. ^ ib. ib. 



