98 REPORT — 1869. 



On some New Forms of Graptolites *. 

 By H. Alletne Nicholson, M.D., D.Sc, M.A. 



In this comniuuication tlie author described twelve new species of Graptolites, 

 which had recently come under his notice. Of these, six were from the Skiddaw 

 Slates, raising the total number of Graptolites from this formation to thirty-four. 

 Three were from the Graptolitic Mudstones of the Coniston series, making, with 

 those already described by the author, a total of twenty-seven species (see Quart. 

 Journ. Geol. Soc. vol. xxiv.). The remaining three were from the Upper Llan- 

 deilo rocks of Dumfriesshire. 

 The following is a list of the species here described : — 



Trigonograpsus lanceolatus. DiplogTapsus Hughesi. 



Dichograpsus fragilis. sinuatus. 



annulatus. Graptolites argenteus. 



Didymograpsus fasciculatus, Diplogi-apsus insectiformis. 



Diplograpsus Hopkinsoni. bimucronatus. 



armatus. Climacograpsus innotatus. 



Sketch of the Granite of the Northerly and Easterly Sides of Dartmoor. 

 By G. Waeeing ORifEEOD, M.A., F.O.S. 



The district known popularly as "Dartmoor" consists of the forest of that 

 name, and portions of the adjoining parishes ; it is estimated as being twenty-two 

 miles from north to south, and twenty from east to west, and is formed of granite 

 or granitoid rocks. The gi-anite, for the most part, is a coarse-grained mixture of 

 quartz, felspar, and mica, which is sometimes white ; large crystals of felspar are 

 often seen, and schorl or tourmaline is of very frequent occurrence both in veins 

 and as an integral part of the rock ; near Chagford the author has found scapoHte. 

 The granite to the north of the Teign is more crystalline than that to the south of 

 that river. The rock-basins, with very few exceptions, are in the district south 

 of the Teign. Perpendicular j oiuts often occur ; tlie greater part have a direction from 

 N.N.W. to S.S.E., and other lines run at right angles to these. The joints that 

 have an easterly and westei-ly dfrection vary more from the perpendicular than 

 the others. Minor lines of joints, which cross at rather acute angles, give a ba- 

 saltiform character to the rocks in which they occur ; these occupy only small 

 areas. The sides of joints are sometimes smooth and shining, and of a dark co- 

 lour, caused by schorl, and the faces are occasionally intersected bj' numerous 

 minute lines, which penetrate about an inch. The beds of granite rarely exceed 

 2 feet in thickness, and the adjoining beds, whether horizontal or pei-pendicular, 

 often differ in character. The division of granite into tabidar masses and beds 

 having a stratiform appearance, is very general ; and the beds are occasionally seen 

 to curve beneath the schistose rocks (as near Belstone Tors)^ and to dip to the valleys 

 on each side of the range, probably causing the contour of the district, as at 

 Kestor and Middletor, between the North and South Teigns. To the south of the 

 Teign a spheroidal structure occurs, and masses resembling boulders are seen in 

 situ in deca^-ing granite ; a good example exists near the Lustleigli Station, and to 

 this peculiar structure the forms of the gi'anite masses, often regarded as trans- 

 ported blocks, is in a gi-eat degree to be attributed. The Elvans of Dartmoor do 

 not equal those of Cornwall either in size or extent ; veins of gi-anite of the same 

 composition as the adjoining gi-anite often penetrate the neighbouring sedimentary 

 rocks ; these can be studied near Chagford, on the left bank of the Teign, at Hunt's 

 Tor and Sharpy Tor; at Sharpy Tor the vein is about 18 feet wide, and contains 

 large crystals of felspar, and masses of the adjoining carbonaceous rock. Veins of 

 porph^-i-y rarely occur ; a vein of coarse poq^hp-y containing pseudo-opal is ex- 

 posed in the farmyard at Forder near Easton, and" also at Sandy Park ; and a vein 

 of fine-gi-ained porphyry may be seen on the old road from Moreton Ilampstead to 

 Exeter, near the cross of the roads at the top of the hill. The decay of gra- 

 nite was next noticed ; various particulars as to granite-gravel were pointed out, 



» Published in extenso in ' Annals and Magazine of Natural History ' for Oct. 1869. 



