GEOLOGY AND MINERALOGY. 49 



difference. Where, however, the pleurae are bent, the length of the side lobes 

 can rarely be estimated with any great exactness. 



The average adult size of these trilobites appears to be about 4-J inches in 

 length, by about 3 inches in breadth ; but, judging from isolated fragments, 

 larger individuals no doubt occur. Many of the Whitby specimens, at the same 

 time, are much below the above dimensions. Most of them are converted into 

 iron pyrites. The Asapkus Barrandi of Hall appears to be a closely related 

 species. 



FOSSILS FROM ALTERED ROCKS IN EASTERN MASSACHUSETTS. 



A very interesting discovery of a trilobite — a species of Paradoxides — in the 

 metamorphic rocks of Quincy and Baintree, about ten miles South of Boston, has 

 just been announced to the scientific world, by Professor W. B. Rogers. The true 

 place of these rocks, hitherto of uncertain paleozoic range, would thus appear to 

 belong to quite the base of the Silurian series : at least if the trilobite in question 

 be really a paradoxides — in which case, it will also be of interest, as constituting 

 the first true specie3of that genus met with in American rocks since the announce- 

 ment of Green's debatable Paradoxides Harlani in 1832. Full particulars of this 

 discovery will be found iu the last October number of the Edinburgh New Philoso- 

 phical Journal; and in the Proceedings of the Natural History Society of Boston, 

 for the same month. 



BURR-STONE. 



A curious deposit of Burr-stone, constituting a vein of considerable thickness, 

 has lately been discovered by Sir William Logan, in the gneiss of Chatham, in Ca- 

 nada East. The stone, probably a siliceous deposit from heated waters, occurs-, 

 according to Sir William, in close association with several complicated veins of 

 igneous rock of at least three different periods of formation. As the stone is of 

 excellent quality, and readily obtainable, the discovery — apart from the scientific 

 interest belonging to the mode of occurrence of the deposit — is one of no little 

 importance. Specimens may be seen in the Museum of the Geological Survey at 

 Montreal. 



RED OXIDE OF COPPER. 



Mr. James Gilbert, lately returned from California, has presented to the Insti- 

 tute, some specimens of red copper ore from the Arizona mines, 110 miles S. E. of 

 Fort Yunia, and about 35 miles from the River Gila. As samples, the specimens 

 are extremely rich, being almost free from rock matter. They contain small 

 strings of native copper, from which the Cu 2 has evidently been derived; and. 

 by a further process of alteration, the ore is converted externally, into malachite, 

 The occurrence of red copper in California has not hitherto been announced in 

 any of our treatises on Mineralogy. We are ignorant of its geological associations. 



VANADINITE. 



In the last number of the Journal, (vol. 1, page 553), an analysis, by Rammels- 

 berg, of Vanadinite from Windisch-Kappel, was given; the results of which lead 

 to the inference tbat VO 3 and PO s are isomorphous. Adolf Kengott, (in Poggen- 

 dorff's Annalen, 1856, No. 9), has subjected this analysis to a very elaborate 

 discussion, in which he seeks to maintain that the loss of 3.21 per cent, therein 

 exhibited, must be due to some cause other than accidental. To account for this 

 loss, he assumes the original existence in the mineral of the hypothetical com- 

 YOL. II. — D 



