FROM THE PURBECK OOLITE. 655 



This was the first example of an upper jaw with teeth of a fossil mam- 

 mal obtained from any secondary rock, and only five"^ suclr jaws were 

 procured by Mr. Beckles when the entire number found by him had 

 amounted (March 20th) to twenty-eight. The other seven specimens 

 found at Purbeck by Mr. Brodie, consisted in like manner of lower jaws ; 

 and the same may be said of the ten specimens (belonging to four spe- 

 cies) of oolitic mammalia hitherto discovered at Stonesfield. 



That between forty and fifty pieces or sides of lower jaws with teeth 

 should have been found in oolitic strata, and with them only five upper 

 maxillaries, together with one portion of a separate cranium, Avill natu- 

 rally excite surprise. f There are no examples of an entire skeleton, nor 

 of any considerable number of bones in juxtaposition. In several por- 

 tions of the Purbeck matrix there are detached bones, often much de- 

 composed, and fragments of others apparently mammalian ; but, if all 

 of them were restored, they would scarcely sufiice to complete the five 

 skeletons to which the five upper maxillaries above alluded to belonged. 

 As the average number of pieces in each mammalian skeleton is about 

 250, there must be many thousands of missing bones ; and when we 

 endeavor to account for their absence, we are almost tempted to indulge 

 in speculations like those once suggested to me by Dr. Buckland, when 

 he tried to solve the enigma in reference to Stonesfield : — " The corpses," 

 he said, "of drowned animals, when they float in a river, distended by 

 gases during putrefaction, have often their lower jaw hanging loose, and 

 sometimes it has dropped off". The rest of the body may then be drifted 

 elsewhere, and sometimes may be swallowed entire by a predaceous 

 reptile or fish, such as an ichthyosaur or a shark." 



We may also suppose that when fish or other aquatic animals attack 

 a decaying carcass, whether it be floating or has sunk to the bottom, 

 they will first devour those parts which are covered with flesh. A lower 

 jaw, consisting of little else than bones and teeth, will be neglected, and 

 becoming detached, may be drifted away by a current of moderate ve- 

 locity, and buried apart from the other bones in sand or mud. 



Among the latest discoveries of Mr. Beckles (March 19th), is the lower 

 jaw of a small, adult, predaceous quadruped, with a robust canine and 

 only six molars, differing in this respect as Avell as in its other characters, 

 so far as the evidence at present extends, from the marsupial type. 



The small average size of the species as yet made out is worthy of 

 notice, the two largest of them not exceeding by more tlian a third the 



-•' The second of these is a fragment of the facial part of the cranium of Tri- 

 conodon, received from Mr. Beckles, February 18th. It consists of the right 

 maxillary bone, containing some of the molar teeth, together with a consider- 

 able portion of the palate uncrushed. 



t As specimens of mammalia are aiTiving weekly from Mr. Beckles, we may 

 expect a great addition to the number of individuals, as well as an increase in 

 the number of species, before his labors terminate. To gain access to these 

 treasures, he has already at his own cost removed nearly 3000 tons' weight of 

 stone overlying the bed No. 93. 



