Prof. T. Rupert Jones — An Annelid Bed in the Gault. 117 



take a wide and scientific meaning for granite — such as that in part 

 adopted by Macculloch — these rocks should be included among the 

 granitic rocks ; or at least considered passage rocks between the 

 basic and granitic rocks. Such rocks, as far as my experience goes, 

 always contain more or less mica and quartz, and when they are 

 capable of being examined in depth, the pyroxenic minerals are 

 found to be gradually replaced by amphibolic; and such a rock, 

 consisting of a crystalline aggregate of felspar, amphibole, mica and 

 quartz, must be called a hornblendic granite. This seems to be the 

 case in the country around Oarlingford (referred to in my former 

 communication), as the Slieve Fag rock (which in places might be 

 called a coarse gabbro, in others a hyperite) seems to graduate into 

 a hornblendic elvanite. 



In the field a twofold division of the igneous rocks into highly 

 siliceous and basic, is found very unsatisfactory. There are certain 

 rocks called Eurytes by Daubuisson, Hybrid rocJcs by Durocher, also 

 including the Trachydolerites of Abich, that partake of the nature of 

 both the felstones and whinstones. Such rocks often occur as bedded 

 sheets, parts of a bed being a rock that must be called a felstone, 

 while other portions are a rock that must be called dolerite, or 

 some other variety of whinstone ; or, as is often the case, the lower 

 portion of the bed will be more felspathic than the upper ; but in 

 either case, whether the change is vertical or horizontal, one kind of 

 rock graduates imperceptibly into the other, so that it is impossible 

 to draw hard boundaries between them. On the Government maps in 

 these cases, of late, the colour for the siliceous is blended into that 

 for the basic rocks. If, however, such rocks were in a separate 

 group, and had a colour for themselves, the work would be more 

 complete. 



In reference to hottleite, Mr. Allport places it in his "acidic 

 group," and says the name is "synonymous with trachalite." The 

 rock trachalite I do not know, but I find that in 1826 Breithaupt 

 described a rock which he called "Tachylyte" (Ta')(y(; Xyrc;), which 

 seems to be the same as the County Down hottleite. In that county 

 this rock, in places, margins and graduates into dykes of dolerite, 

 and apparently belongs to the basic group of the igneous rocks. 



IV. — Note on an Annelid Bed in the Gault of Kent. 

 By Prof. T. Eitpert Jones, F.R.S., etc. 



THEEE is a peculiar band, full of Annelid borings, in the Gault of 

 Kent, which does not appear to have been recorded in the 

 papers on the Gault of Folkestone, by Mr. De Eance, in the Geol. 

 Mag. 1868, Vol. V. p. 170, etc., and Mr. Price, Quart. Journ. Geol. 

 Soc. 1874, vol. XXX. p. 344, etc. It may possibly, however, be one 

 of the "hard bands" noticed in their sections, but not described in 

 detail. In 1866 I collected some specimens of this Annelid Bed in a 

 Gault pit, dug for brick- and tile-making, at Westwell Leacon, a 

 mile and a half S.W. of Charing, Kent. It was about two inches 

 thick, continuous across the pit, red in colour, with bluish pipings 



