312 



THE GEOLOGIST. 



" It may here be remarked that the types of igneous rock, which hare 

 here been deposited contemporaneously with the sedimentary strata, are 

 found to be very similar to those of the intrusive rocks of other parts of 

 the county, e.g. of Doonan Hill, close to the town of Donegal, 



" On passing west from Buncrana towards Dunaff Head, through the Gap 

 of Mamore, it is found that, as we approach the granite at Urrismenagh, 

 the dip of the beds increases from 45° to nearly absolute vertically. The 

 granite of Urrismenagh does not present many features of interest to the 

 mineralogist, as the rocks in immediate contact with it are quartzose, and 

 therefore unlikely to yield accidental minerals. . . . The chief point which 

 is noticeable about the neighbourhood of Dunfanaghy is the extreme de- 

 velopment of a highly crystalline syenite, containing a very large propor- 

 tion of titaniferous magnetic iron. The octohedral crystals of this mineral 

 are very noticeable on the weathered surface of the rock." 



Hybodus and other Fossils. — Dear Mackie, — A few notes on ' Geo- 

 logist,' No. 67. — P. 241. Many specimens of shark-jaws much like, if not 

 the same as, Hybodus basanus, certainly in similar state of preservation 

 and matrix, occur in the Wealden beds near Hastings, probably in the 

 middle portion of the Hastings sand series. Mr. Moore, of Hastings, and 

 Mr. Beckles, have collected several specimens. The Wealden beds below 

 the Perna bed (bottom of the Lower Greensand) in the Isle of Wight 

 present about 100 feet of thickness above the equivalent of the Hastings 

 sand ; therefore, if occurring there in the equivalent of the Hastings series, 

 the Hybodus may have been found perhaps on the shore not far from the 

 junction with the Lower Greensand ; nevertheless it may be truly a fossil 

 from the latter. 



Page 243, etc. — " Lias Bone-bed." You might as well give the proper 

 term to this at once, " Rlicetic Bone-bed " (or " one of the bone-beds of the 

 Upper Keuper"). The Rhastic shales at Linksfield, near Elgin, are also 

 rich with Hybodus. The Linksfield shales, at first thought to be Wealden, 

 were referred by Morris to the Great Oolite, but are now regarded as 

 Ehsetic. See my monograph on Fossil Etherise, p. 77. Sphenonchus 

 Martini, Ag., also from Linksfield, is regarded by Ogilvie and Charles- 

 worth as the " frontal spine " of Hybodus. 



Page 245. — In your list, after Morris, you should have kept H. stria- 

 tulus to the Wealden. It would have been well if you had separated 

 teeth from spines in the list. 



Page 255. — " Rhinoceros Etruscus." I do not see this mentioned in 

 M. Desnoyers' Memoir. 



Page 267. — Why didn't you notice the fact of Sir P. Egerton and Mrs. 

 Smith's specimens of DoUchosaurus being parts of one and the same spe- 

 cimen? See Dixon, Foss. Suss. p. 388, Owen's Monog. Cret. Eept. 1851, 

 p. 22, and Medals, p. 712. 



Page 268. — " Lower Greensand Reptiles." I believe that the little cro- 

 codile figured and described by Owen, Monog. 1851, p. 45, as in Saul's 

 collection and from the " Lower Greensand, near Hastings," was from the 

 Wealden. I saw it in Saul's collection. 



Page 270. — " Lapis frumentarius." "Lapides frumentarii" are pieces 

 of Numinulitic limestone, Alveolina limestone, and stone full of other 

 Foraminifera, as the case may be, with different old authors. The sections 

 of the Nummulites present occasionally seed-like appearances as well as 

 small leaf-like objects, which latter gave rise to the terms " Salicites," 

 " Daphnis," etc. ; whilst the Alveolina?, etc., were thought to be rice 

 and other grain, as millet, fescue-grass, etc. Hence the names " Phacites," 

 "Seminales lapides," " Lentes lapideaV " Lapides cumini, frumentarii," 



