296 Mr. G. KrefFt on a new Species of Thylactne. 



he still holds to his original assertion as to the existence of 

 perforations in these shells. 



When Prof. King shall have shown the least ground for 

 the belief that shell-tissue of the most peculiar and charac- 

 teristic kind can be formed during the process of fossilization, 

 so as to fill vacuities that existed in the recent shell (which is 

 just as if, in the silicification of a piece of wood previously 

 perforated by large holes, these holes should be filled up by 

 true woody tissue), his assumption that the whole of Mr. Da- 

 vidson's type specimen of Spirifer cuspidatus and that the 

 imperforate spaces in the shells of SyringotJiyris were origi- 

 nally perforated may deserve consideration. Until then, I 

 venture to think that the imperforateness of the former type, 

 and the patchiness of the perforations in the latter, are esta- 

 blished by Prof. King's confessed inability to set aside the 

 facts stated by me on these points, as the direct results of 

 careful and experienced observation. 



Trusting that this is the last occasion on which I shall feel 

 it necessary to address you on this subject, 



I remain. Gentlemen, 



Your obedient Servant, 



William B. Carpenter. 



XXXV. — Description of a new Species of Tliylacine (Thyla- 

 cinus breviceps) . By Gerard Krefft, Curator and Secretary 

 of the Australian Museum, Sydney. 



[Plate XVn.] 



Skull shorter (6f inch.) than that of T.cynocephalus {1\ inch.) ; 

 the palatal openings much reduced in size ; occipital foramen 

 larger than in the well-known species. The anterior part of the 

 skull is not much compressed ; and the sharp nick so prominent 

 in all skulls of T. cynocephalus^ between the second and third 

 premolars, is wanting in the present species. The greatest dif- 

 ference exists in the teeth, which in the new species are veiy 

 large, the most prominent being the second and third molars 

 in both jaws. The canines are thicker, and form a shorter 

 curve ; the outer incisor of the upper series is also very much 

 larger than the corresponding tooth in T. cynocephalus, 



I enclose three photographs of the skulls of both animals* 

 in different positions, both very perfect, and that of T. cyno- 

 cephalus larger than that of the new species. The last molar 

 in T. hreviceps has been lost from both specimens (in posses- 

 sion of the Trustees of this Museum) ; but the sockets indicate 



* We have given in the I^late the figures of the new species only. — Ed. 



