254 



MESSES. E. H. RA STALL AND J. ROMANES ON [Aug. I909, 



specimens, but have not been able to come to any general conclusions 

 as to their place of origin. 



As typical examples of the assemblage of boulders to be found in 

 gravel-pits near Cambridge we append lists of rocks recognized in 

 two cases : (i) a pit on the golf-links near the summit of the 

 Gog-Magog Hills ; and (ii) a pit now being worked on the 

 Huntingdon Road, near the Traveller's Rest, about a mile from 

 Cambridge. 



(i) Pit on Summit of Gog-Magog Hills. 



Rhomb-porphyry [2]. 



Felspar-porphyry. 



Grey granite. 



Forfarshire porphyry. 



Cheviot porphyrite and andesite. 



Lavas of Scottish Carboniferous or 



Old Red Sandstone type. 

 Dolerite 1 1 -, , 

 Basalt } ab ™ danfc - 

 Old Red Sandstone. 

 Carboniferous Limestone. 

 Millstone Grit. 

 Great Oolite Limestone. 



Oxford Clay (concretions with Ser- 



pula tetragona). 

 Bunter pebbles. 

 Carstone. 

 Boxstones. 

 Hunstanton Red Rock and pale pink 



Chalk. 

 Bored Gryphseas. 

 Large grey tabular Lincolnshire 



Flints. 

 Very abundant rounded pebbles of 



hard white Chalk, of northern type. 



(ii) Pit on Huntingdon Road, near the Traveller's Rest, 

 1 mile from Cambridge. 



Gravel with sandy seams and brown pipes of the ordinary type. Dr. Bonney 

 thinks that it is more like the plateau-gravels than the Cambridge terrace- 

 gravels. Large boulders are unusually numerous, measuring up to 1 cubic foot. 

 The great majority are sandstone, probably Carboniferous, but other rocks are 

 fairly common. The following are identified, and confirmed by Dr. Bonney : — 



Carboniferous Limestone, several, 



some striated. 

 Millstone Grit, several. 

 Basalts 1 large and unusually well 

 Dolerites J rounded. 

 Rhomb-porphyry [2]. 

 ?]S'ordmarkite. 

 Pink granulitic granite, two large \ 



specimens. 

 Orthophyre, of North Berwick type. I 



? Analcime-dolerite (teschenite) of 

 Forth Valley type. 



Cheviot porphyrite and lava. 



Coarse white granite. 



Crushed gneiss. 



Large concretion with Serpula tetra- 

 gona. 



A species of Gryphcea, intermediate 

 between arcuata and dilatata. 



(2) Hardwick and St. Neots Road : 52 specimens. 



From this district only a small number of specimens have been 

 obtained, mostly from arable land, since there are no gravel-pits. 

 Among these a large proportion are easily recognizable, including 

 the following important types: — one rhomb-porphyry, one alkali- 

 syenite, and one segirine-granite ; four specimens of porphyry as, and 

 three of the Forfarshire porphyry. Five specimens are of Cheviot 

 type, and one which was sliced is of especial interest, since it seems 

 to be closely allied to the mugearite-type of Mr. Harker, which is 



