1862.] FALCONER PLAGIAULAX. 363 



With reference to the angular process, I have nothing to add to 

 what is set forth in my former communication. This process, which 

 is a verj^ constant character of the carnivorous jaw, is wanting as a 

 salient apophysis in Plagiaulax, although well developed in the minute 

 insectivorous Myrmecohius. 



I have one remark more to make in reference to the form of Pla- 

 fjlaidax. Fig. 15 of my original description gives a representation 

 of what remains of the lower jaw of P. minor, magnified to a scale 

 of four diameters. The entire length of the specimen, including the 

 six molars and premolars, together with the procumbent incisor 

 (according to the metrical line e), does not exceed -4 of an inch, of 

 which the six cheek-teeth united make only about two and a half 

 lines (-25 inch). I ask any zoologist or comparative anatomist to 

 look at it, and say whether the dental apparatus of this extremely 

 minute creature is competent to perform the duties required of a pre- 

 daceous carnivore. Magnitude in this case is an important ingredient, 

 as it necessarily involves measure of force. Could P. minor have 

 preyed on small jVIammals and Lizards ? Is it not more probable that 

 this pigmy form was itself an object of prey in the Purbeck Fauna ? 



In the preceding observations I have gone seriatim into the ob- 

 jections raised against the view which I advanced of the affinities 

 of Plagiaulaoo. In the work referred to, every detail of external 

 form was regarded in a light different from that in which it was 

 ^dewed by me ; every inference was controverted ; and the conclusion 

 drawn from the whole was diametrically the converse arrived at by 

 me. The verdict of Comparative Anatomists will decide which is 

 right. I have reconsidered my first inferences, and tried to test their 

 vahdity by the strongly contrasted and extreme view put forward by 

 Professor Owen ; and the result has been to confirm the opinion that 

 PJagiaidax did not belong to a carnivorous type of Marsupials. Re- 

 garded morphological!}^, in the plan of its dental system, — rationally, 

 through its condyle and correlated characters, — and empirically, by 

 comparison with Hypsiprymnus and Cheiromys, it has led me, through 

 every aspect, to this conclusion. Enough has been adduced in the fore- 

 going pages to show that, to whatever family comparative anatomy 

 may ultimately consign the genus, it must always be held to be a 

 singularly modified form. I have directed attention to the numerous 

 points of analogy between the lower jaw of Plagiaidax and that of 

 the Aye -Aye, itself one of the rarest and most aberrant of existing 



cavity preventing protrusion or retraction of the lower jaw ; and the muscular 

 power being applied close to the condyle leaves the free part of the lever longer, 

 or, in other words, admits of a wider separation of the jaws in front, for the 

 canines and cutting-teeth to act. In the Aye- Aye and Eodents (e. g. Cavia and 

 Ht/Htrix) the fulcrum is moveable, the condyle playing on a flat glenoid surface ; 

 the point of insertion of the muscular power is more advanced, leaving a short 

 portion of the lever free, and thus restricting tlie aperture of the jaws. These 

 conditions, combined with the oblique direction of the temporal muscle, implied 

 by the reclining coronoid, conspire to produce the antero-posterior and lateral 

 motions required by the regimen of these forms. The same reasoning applies 

 to Plagiaulax. 



