BY THE REV. J. E. TENISOiN'- WOODS, F.U.S. 389 



Mesozoic or earlier tertiary times ; but it would be premature to 

 build any solid theory on these facts. 



The above are general outlines of the Geology and Physical 

 structure of Australia. A closer examination of the details may 

 amplify or elucidate the the conclusions ; but the brief exposition 

 of the facts is made on observations which are not likely in 

 future to be disturbed or changed. 



On a large Mesozoic MytlJns from the Barcoo. 



By the Eet. J. E. Tej^ison-Woods, F.G.S., F.L.S. 



The following specimen was given to me for description by the 

 Hon. A. Archer, of Gracemere, Queensland. The locality from 

 which it was taken was uncertain, but he believed that it was 

 found on the rocky banks of the Upper Barcoo at the foot of a 

 sandstone table] and. It is therefore probably from the edge of 

 the Upper or Middle Mesozoic strata in that locality. The fossil 

 was accompanied with Belemnites and there were no less than 

 two other specimens in Mr. Archer's possession so that I should 

 conclude that it was abundant. It is a very large species of 

 Mytilus, so large in fact that I do not believe any larger has been 

 described. Unfortunately very little of the shelly matter has 

 been preserved and therefore the description refers rather to a 

 very perfect east of the interior of the valves, but as the form is 

 singularly regular and even and the shelly matter thin the details 

 are well preserved and distinct. 



MyTILUS IlfGEXS, n. s. 



M. t. oblong, oval, or elliptical, tumid or gibbous in the centre, 

 so as to form an arched broad regularly sloping carina, depressed 

 at the anterior side, thick, but not clumsy at the posterior margin, 

 the whole very equally sulcate with lines of growth, the younger 

 ones deep ridged and with a beautiful curve, the latter less distinct 



