1857.] FALCONER PLAGIAULAX. 2/7 



The curious fact, that only lower jaws should have turned up 

 among the Stonesfield mammalian remains, has often been the subject 

 of speculation or remark. The same, to a certain extent, has held 

 good with the remains found in the Purbeck beds. Among the de- 

 termined fossils, lower jaws predominate largely. But some upper 

 maxillaries have been met with, and, while writing, I have received 

 intimation of the discovery of more. Among the undetermined 

 remains there is a considerable number of other bones of small ani- 

 mals, many of them probably mammals, but they are seldom or ever 

 perfect. In these minute creatures, unless the bone be complete, 

 and, supposing it to be a long bone, with both its articular surfaces 

 perfect, it is almost hopeless, or at any rate very discouraging, to 

 attempt to make out the creature which yielded it ; whereas the 

 smallest fragment of a jaw with a minute tooth in it, speaks volumes 

 of evidence at the first glance. This I believe to be one great reason 

 why we hear so much of jaw-remains, and so little of the other bones. 

 For, as an inferior maxillary is to the other bones of the skeleton in 

 the ratio of about 1 to 2.50, cceteris paribus, a large number of these 

 should be encountered for every lower jaw that turns up. No indi- 

 cation has yet been met with at Purbeck of the bone of a good-sized 

 terrestrial mammal. But I do not consider the negative evidence in 

 this case to be decisive of their non-existence. The matrix of the 

 so-called " Dirt-bed No. 93," by which most of the mammal remains 

 have been yielded, is a whitish-grey, fine-grained marl, full of the 

 exuviae of freshwater animals, hardening into a kind of stone when 

 the moisture is expelled by desiccation, but very bibulous, and readily 

 becoming pasty, after immersion in water. It has properly no claim 

 to the designation of a "dirt-bed," or "ancient vegetable soil," as 

 there is rarely a speck of vegetable matter to be seen in the numerous 

 specimens containing bone-remains which have passed through my 

 hands*. It appears to me to present more the character of the deposit 

 near the margin of a patch of fresh water, and that the probable 

 explanation of the association of so many small bones of minute 

 mammals and lizards is that they were the floating objects most 

 readily drifted to the margin by a surface-ripple from wind, or by a 

 wave-eddy. In India, in the tanks, or wherever running water falls 

 into an artificial lake, numerous remains may be observed along the 

 margin, of the bones of frogs, lizards, mice, and musk-rats, forming 

 a more or less continuous edging, without the admixture of large 

 bones, which lie in abundance below the deeper water. The former 

 float and are drifted to the margin by the action of the wind, and 

 rest there. 



M. Lartet pointed out to me, in the rich Falunian deposit of 

 Seissan, certain parts of the lacustrine bed where skeletons of large 

 terrestrial animals, such as Mastodon and Rhinoceros, are more or 

 less abundant ; while in other situations near the margin immense 



* I am informed by the Assistant-Secretary, however, that the hand-specimens 

 of this bed, in which Spalacotherium occurred in 1854, were of a dark colour and 

 contained vegetable remains, together with freshwater shells. See Quart. Journ 

 Geol. Soc. vol. X. p. 423. 



