Jenkins— On an Australian Trigonia, 201 



more likely that Stylodon, like Spalacotherium, and Chrijsochloris 

 (unique in. this respect among existing Insectivora), exemplified that 

 excess of number of teeth, which, in Marsupialia, as in Insectivora, 

 is seen in a single known existing genus {Myrraecobius) , but was 

 common in the similar small insectivorous pouched mammals of the 

 older OoKtic deposits. Spalacotherium had ten molar teeth on each 

 side of the lower jaw, of which the last six had tricuspid crowns, 

 with proportions and spacing similar to those in the Cape mole.^ 

 The corresponding teeth of the present genus and species are in 

 closer contact with each other, and are of more simple shape, and 

 apparently more simple implantation. 



The grounds for adding another genus and species to the Purbeck 

 Mammalian catalogue {Spalacotlierium, Triconodon, Plagiaidax) are 

 sufficient, and also, as it seems to me, to determine the genus to have 

 been either less- or ly- encephalous ; but, with the known range of 

 diversities of dental character in recent and extinct marsupial and 

 placental Insectivora, I feel a need of further evidence before pro- 

 nouncing on the sub-class or order of Stylodon. 



EXPLANATION OF PLATE X. 



Pig. 1. — Portion of lower jaw and teeth of Stylodon pusilj,us, Ow., as embedded in the 



matrix, nat. size. 

 Fig. 2. — The portion of jaw and eight teeth in place, magnified three times. 



III. — On the Ocoijkrence of a Eeoent Species of Trigonia (T. 

 Lamarckii) in Tertiakt Deposits in Australia. 



By H. M. Jenkins, F.G.S. 



(PLATE X., Figs. 3-7.) 



IN No. VI.- of the " Quarterly Journal of Science " I gave a brief 

 account of the Trigonia semiimdidata, M'Coy, MS., which has 

 been found in certain Tertiary strata in the Colonies of Yictoria and 

 South Australia, and which had been named, but not described, by 

 Professor M'Coy. This species differs altogether from the recent 

 forms, and approaches very closely in its essential characters to the 

 members of the gTOup " costata," characteristic of the Oolites. It 

 was therefore remarked, in the communication referred to, that its 

 occurrence in Tertiary strata in Australia added another link to the 

 chain of evidence which connects the recent fauna of that region 

 with the Oolitic fauna of Europe. But doubt may be expressed as 

 to the exact value to be assigned to this similarity in facies between 

 two faunas so widely separated in time; and it is a fair question 

 whether the discovery of this Trigonia does not diminish, rather than 

 add to the apparent peculiarity of the existing Australian fauna. 



Having recently received a large collection of fossils from the 

 Tertiary strata of Victoria, and the specimens having been collected 

 and labelled by the officers of the Geological Siuwey of the colony, 



1 Proceedings of the Geological Society of London, June 1854, p. 425. 



