A discussion has more than once arisen, in the course of the last two years, respecting the true position or the quartz conglomerate exposed near Twt Hill, Carnarvon, which was first described by Prof. Bonney and Mr. Houghton in the Quarterly Journal of the Geological Society, vol. xxxv. p. 321. The typical quarry is situated on the S.E. side of the ridge, close underneath Twt Hill, and the exposure there shows the quartz conglomerate in juxtaposition to the granitoid rock that constitutes the axis of the ridge. The authors describe a passage between the granitoidite below and the conglomerate above, and state that the latter “passes lip into a rock which has some resemblance to the bottom rock” (granitoidite). In the GEOL. MAG. for March, 1880, p. 118, Dr. Callaway writes: “Messrs. Bonney and Houghton have detected at Twt Hill a passage between the granitoidite and a quartzose conglomerate with a S.E. dip. I have visited this section, and having examined the rock inch by inch, I can entirely confirm their identification.”