20 Prof. T. Rupert Jones — Canadian Ostracoda. 



These analyses show that if this Dinas Head rock be an adinole 

 it contains a larger per-centage of soda than any adinole hitherto 

 analysed. 



Schenck found in the Hartz adinole 7*14 per cent, of soda in 

 one specimen, and Kayser ' found 7-54 per cent, of soda in adinole 

 next the diabase. 



That the greenstones of the Dinas Head district contain enough 

 soda to account for the impregnation of sedimentary rooks into 

 which they have intruded may be inferred from Mr, J. A. Phillips' 

 analyses of many so-c,alled greenstones in North and Central 

 Cornwall, published in the Quart. Journ. Geo!. Soc. for 1878, in 

 which he records several of them as containing over 5 per cent, of 

 soda ; one as much as 5-84 per cent. 



Supposing the Dinas Head rock to be an adinole, two difficulties 

 have to be met : How does it become interstratified with slate ? 

 How do the spherulitic and concretionary structures arise ? 



Mr. Teall informs me that the presence of ferriferous carbonate 

 favours the theory of its being an altered sedimentary rock, whilst 

 the spherulitic and concretionary structures favour the theory of its 

 being an igneous rock, viz. a soda felsite or keratophyre. 



I am not prepared to explain the origin of this rock, but it is 

 certainly of interest on account of its remarkable composition. 



IV. — On some Fossil Ostracoda from Canada. 

 By Prof. T. Eupekt Jones, F.R.S., F.G.S., etc. 



(PLATE II.) 



Contents. 



§ 1. Introduction. 



§ 2. Description of tlie Species. 



I. Pleistocene. EoUing River. 



1. Canclona Candida (Miiller). 

 ? Ilyohates reptans (Baird). 



2. Cytheridea Tyrrellii, sp. nov. 



II. Loose block. Milk Biver. 



3. Fotitocypris pyriformis, sp. nov. 



4. Cypris Dmvsoni, sp. nov. 



5. Ilyocypris oblonga, sp. nov. 



III. Saint-Mary-Eiver Beds. Milk River. 



6. Cythere, sp. indet. 



7. Candona (H) Sanctce-Marim, sp. nov. 



8. Cytherella criicifera, sp. nov. 



IV. Saint-Mary-Eiver Beds. Old-Man River. 



9. Candona (?), sp. indet. 



§ 1. Introduction. 



THE specimens here referred to belong to the Geological Survey 

 of Canada, having been collected — I. some (of Quaternary 

 age) by Mr. J. B. Tyrrell, B.Sc, F.G.S., in 1887, on the Boiling 

 Eiver two miles above Heart Hill in Manitoba. 



n. Small pieces of a loose block, lying by the South Branch of 



1 Kayser, Hartz Z. Geol. Ges. xxii. 1870, p. 103. 



