GEOLOGY AND MINERALOGY. 483 



cephalus, at least in aluit individuals, is the comparatively undivided character of the 

 caudal shield. In the Whitby schists, however, trilobites occur, over seven or eight 

 inches in length (if not longer,) with the caudal extremity not only distinctly tri- 

 lobed, but also marked with numerous and distinct pleura? extending almost to the 

 edge of the striated limb; whilst at the same time, they agree in all other respects 

 with A. platycepkalus. In the union of the facial suture above the glabella, for 

 example, the two are alike ; and in the peculiar character of the body-segments and 

 pleura), not the slightest difference is perceptible. As no figure of this trilobite is 

 given in Hall's Palaeontology, and as the form appears to differ from the figured 

 European species, we propose to confer upon ic provisionally the name of Asaphus 

 Canadensis. If it be really new, it may be placed as the type of a particular sub- 

 -division of the Asaphidae, in accordance with the following scheme : — 



Asaphidit with facial sutures united : 



§1. Pygidium, undivided: — Type, A. platycepkalus. 



§2. Pygidium with grooved axis : — Type, A. expan -us. 



§3. Pygidium with grooved axis and pleura : — Type, A. Canadensis. A drawing 

 of this latter species will be given in the second part of our Paper on the 

 Trilobites. 



MINERAL0G1CAL NOTICES. 



Dufrenoysite : — Ch. Heusser has communicated to Poggendorff s Annalen (1856, 

 No. 1.) some additional information on the crystallization of Dufrenoysite 

 [2 (PbS) + As 2 S 3 ] from the dolomite of the Binnenthal. He confirms the Mono- 

 metric character of the mineral; but, in addition to the forms hitherto discovered, 

 vis: — the rhombic dodecahedron, and the leucitoid 2-2, he announces the cube, the 

 octahedron, a second leucitoid 6-6, and a trisoctahedron ^. Hardness, 4-5 



Binnite: — Heusser has also subjected to a detailed examination, the steel-grey 

 metallic sulphide which often accompanies the Dufrenoysite at the above locality. 

 This mineral has been known in Switzerland for some time under the name of Bin- 

 nite. It occurs in very small and longitudinally striated prisms of extreme brittle- 

 ness. Streak, dark-red, much darker than that of Dufrenoysite ; specific gravity 

 (according to an earlier determination of Von Waltershausen on specimens taken 

 by him for Dufrenoysite) = 4-4*77. These latter specimens, according to Uhrlaub, 

 contained sulphur, arsenic and copper, with a mere trace of lead. The system of 

 crystallization of Heusser'9 specimens, was apparently Trimetric, but the prism-angle 

 could not be obtained, owing to the striae on the faces. The measured angles, 

 those of a series of domes, but whether macrodomes or brachydome3 not determi- 

 nable, did not accord with the measurements obtained by Von Waltershausen. An 

 examination of further specimens is consequently desirable. 



Hyalophane : — The dolomite of this same locality furnished to Von Waltershausen 

 another mineral, which he described as new, under the name of Hyalophane. It 

 was thought tc contain : SiO 3 , A1 2 ; \ CaO, MgO, NaO, BaO, SO 3 , and 110. Heusser 

 has shewn, however, that it is simply an adularia variety of Orthoclase, containing 

 accidental particle3 of Iron pyrites, and interpenetrated by Dolomite and Heavy 

 Spar. Seven distinct crystals carefully freed from these impurities, and tested 

 respectively by the blowpipe, did not yield the slightest trace of sulphur. 



Rhodonite:~ Crystals of the Silicate of Manganese, or Rhodonite, are, it is well- 

 known, of rare occurrence. From those hitherto met with, and from the cleavage 

 planes of massive specimens, the crystallization of the mineial has been long con- 

 sidered identical with that of Augite or Pyroxene : a supposition apparently cod- 



