Vol. 65.] THE BOTJLDEKS OP THE CAMBRIDGE DKIFL 257 



Barrington and Foxton district and as identical with the quartz- 

 porphyry of Buchan Ness (Aberdeenshire). 



Two specimens are referred to the Central Valley of Scotland ; 

 a slice cut from one of these was identified by Mr. G. Barrow as 

 the analcime-dolerite (teschenite) of Car Craig, Firth of Forth. A 

 boulder from Pampisford gravel-pit proves to be an unusually 

 fresh example of a very basic lava ; it is a porphyritic rock, with 

 phenocrysts of olivine and augite set in a ground-mass of augite 

 and deep brown glass, with a few laths of felspar. This agrees 

 in every respect with the well-known limburgite of Whitelaw Hill 

 (Haddingtonshire), originally described by Dr. Hatch. 1 The Cheviot 

 type is here strongly represented, there being thirteen specimens. 



The sedimentary rocks include Millstone Grit and silicified 

 oolite, together with the assemblage consisting of Bed Chalk, bored 

 Gryphaeas, and bored white Chalk, all of which are abundant here. 



Liver-coloured quartzites from the Bunter pebble-beds are fairly 

 common. Pink granulites are rather abundant ; but the basic 

 igneous rocks form the most numerous group in this district, being 

 represented by seventeen specimens. 



Among the metamorphic rocks, schists are conspicuous by their 

 almost complete absence — only one being recorded, though the 

 gneisses number six. 



A point well worth noting is the similarity between the boulders 

 of this district and those obtained from the pit on the summit of 

 the Gog-Magog Hills, the only important differences being the 

 absence from the latter locality of the Buchan Ness porphyry and 

 metamorphic rocks. 



(7) Chesterford : 22 specimens. 



The collection from this district is small, but most of the types 

 are represented. A rhomb-porphyry, a syenite, and a specimen of 

 Sparagmite may be assigned to Scandinavian origin. The syenite 

 is a semi-plutonic rock of moderately coarse texture, consisting of 

 alkali-felspars (perthite) and a deep brown amphibole, which may 

 be referred to barkevikite. Some subsidiary red biotite (lepido- 

 melane) and colourless augite are also present. The rock is 

 evidently highly alkaline, and may be conveniently named 

 barkevikite-syenite. It has clear affinities with the rocks of the 

 Christiania province. 



One specimen each of the x and Forfarshire porphyries occur. 

 The Scottish rocks are represented by one porphyrite of North 

 Berwick type and two of Cheviot-dyke type. 



The sedimentary rocks include a silicified limestone, Neocomian 

 grit, and Lincolnshire Red Chalk. 



Pink granites and granulites are relatively abundant, and basic 

 igueous rocks also occur. 



1 Trans. Koy. Soc. Edin. vol. xxxvii, 1891-92 (1895) pp. 116-17. 



