98 



Rat-kangaroos would hardly, in that state of division, be fit for swallowing; accordingly we 

 find a provision of not less than sixteen square and broad-crowned, ridged, and tuberculate 

 grinders, superadded to the trenchant teeth, in order to pound up the chopped roots and 

 grass, and to well blend those dry vegetable cuttings with abundant salivary secretion, in 

 order to prepare a bolus fit for deglutition and subsequent digestion. 



§ XIX. Objections to the Carntvority of Plagiaulax examined. 



Fig. 1G. 



The procumbent pair of lower incisors in Pocphaga oppose the upper surface, not the 

 end of the tooth, to three pairs of upper incisors, of which the foremost is longest. By the 

 analogy of Thylacoleo the suberect pointed pair of lower incisors in Plagiaulax would be 

 crossed by a correspondingly developed and deflected pair of laniariform incisors ; and, if 

 these were followed by others in the premaxillary bones, they would probably be rudimental 

 and limited, as in Tlnjlacolco. to a single pair. 



The functional incisors in both jaws would act as in Thylacoleo, the lower ones like a 

 pair of bayonets, cemented side by side, with the muscular forces of 

 both mandibular rami concentrated on the thrust. A like advantage 

 in lethal stabbing power is gained by the same " collateral arrange- 

 ment in the axis of the perforating stroke, in many of the Ferines 

 filt (" Carnassicrs ") of the Cuvierian system. It is interesting to note, 



] fx ■) however, that these instances occur in the orders (' Insectivores, 



Marsi/piaux') which I have proposed to place, through cerebral 

 characters, on low r er steps in the Mammalian series; the lissen- 

 cephalous and lyencephalous conditions of brain seeming to me of 

 greater taxonomic value than the " possession of claws and of three 

 kinds of teeth." 2 With lower intelligence the power of the killing 

 teeth is heightened; and a like relation is not unfrequently exemplified. 



Observation of the habits and actions of the lissencephalous Otter 

 {Potawogale, Du Chaillu), with approximate or " collateral " laniaries 

 (fig. 16), shows them to be as efficient, to say the least, in the capture and slaughter of its 

 prey, as are the divaricate laniaries in the gyrencephalous Otter {Lufra). The Hedgehog 



1 Falconer, "On tbe disputed Affinity of the Mammalian Genus Plagiaulax from tlie Purbeck Beds," 

 in 'Quarterly Journal of the Geological Society,' vol. xviii (18G2), p. 3.12 ; also, " Palaeontological Memoirs," 

 vol. ii, p. 435. 



- " Les Carnassiers forment une reunion considerable et varied de quadrupedes onguicules, qui possedent 

 les trois sortes de dents." Cuvier, ' Regne Animal,' torn, i, ed. 1829, p. 1 10. But see, Owen, "On the Charac- 

 ters, Principles of Division, and Primary Groups of tbe Class Mammalia" in 'Proceedings of the Linnean 

 Society,' Feb., 1857 ; also, "Anatomy of Vertebrates," 8vo, vol. ii, p. 296. 



3 I am indebted for the drawing from which cut fig. 1 G was taken to Prof. Allman, F.R.S., of the Uni- 

 versity of Edinburgh, where the unique skeleton of that rare genus is preserved. 



Front view of upper 

 and lower incisive 

 laniaries, Polamogale 

 velox ; twice nai. size. 3 



