BY W. N. BENSON. 699 



further details of tlie fiel(i-occui-reiice, chemical composition, etc., 

 of tliese limestones, reference must be made to Messrs. Carne tt 

 Jones' forthcoming work (2). 



In Portion 159, Attuni^a, the western of the two large masses 

 of limestone (carefully surveyed by Lieut. Aurousseau), lias a 

 locally developed, strong contact-alteration. In the dusk of an 

 evening, in 1910, the writer collected a number of specimens 

 from here, but did not work out their field-relationships. These 

 were subsequently described in detail, and, from the occurrence 

 of cassiterite and scapolite in them, it was concluded that they 

 lay near the end of a granitic apophysis with a pneumatolytic, 

 metamorphosing effect. A few felspathic rocks, rich in calcite, 

 etc., suggested- an endogenous alteration of such an intrusive 

 mass(l, 6, pp.7 14-716). Lieut. Aurousseau, however, discovered 

 a vein of lamprophyre invading the limestone, and he believes 

 that it was the cause of the metamorphism. He gives the fol- 

 lowing account of the change of the limestone in the few yards 

 adjacent to the lamprophyre : — i., The dyke; ii., calcite-phlogo- 

 phite rock; iii., dark limestone; iv., phlogophite rock; v.,melanite- 

 woUastonite rock, with clinozoisite, vesuvianite, calcite, mica('?), 

 and pyroxene; vi., vesuvianite-wollastonite rock with a little 

 melanite; vii., saccharoidal limestone. Evidently, the small 

 collection, already described by the writer, is fairly typical of 

 the whole occurrence. The nature of the intrusive rock is not 

 known. There is here, accordingly, an interesting field for study 

 in comparison with Bergeat's descriptions of endogenous and 

 exogenous contact-metamorphism in Mexico (5). 



The only other feature of interest, in the Middle Devonian 

 rocks observed by the writer, is a small mass of vesicular spilite, 

 east of the railway near Somerton Road Station. 



The passage from the Middle to the Upper Devonian beds is 

 not always marked, as was formerly believed, by the develop- 

 ment of an intervening mass of Baldwin Agglomerate. Indeed, 

 the study of the southern part of the Tamworth district shows 

 that passage from the dominantly cherty rocks of the Tamworth 

 type, into the soft mudstones of the l^arraba type, may take 

 place considerably below the base of the Barraba system, marked 



