Prof. Harkness on Fossil Diatomacese. 



145 



cially to the two following facts, viz. First — that, in our own country, 

 many native Lichens, which grow more or less abundantly, might, 

 with advantage and ceconomy, be substituted for the somewhat ex- 

 pensive and scarce foreign Roccellas and other dye-Lichens usually 

 employed in the manufacture of orchil, cudbear and litmus ; and, 

 secondly — that, in our colonies, and foreign countries to which we 

 have access, species valuable as dye-Lichens probably grow in abun- 

 dance — might be collected and transported easily and cheaply — and 

 thus become important and lucrative articles of commerce. 



3. " On Diatomacece found in a Sub-fossil state in Dumfriesshire," 

 by Robert Harkness, Professor of Geology, Queen's College, Cork. 



In this paper, the author remarked: — "WTiile examining the 

 boulder depos^its which occur on the northern shore of the Solway 

 Frith last summer, my attention was directed to a locality about a 

 mile west of the mouth of the river Annan, where there is an inter- 

 esting association of indurated gravel beds, hill deposits, and peat- 

 bog, overlaid by the vegetable soil of the district. The boulder 

 gravel, which here is the lowest deposit exposed, consists of the ordi- 

 nary Silurian sandstone, mixed with the carboniferous grits, and a 

 few fragments of the Bunter sandstone of the neighbourhood. It 

 had a hardened nature, and in this respect bore considerable affinity 

 to many conglomerates. Above this bed of indurated boulder gravel 

 there is seen a silty deposit, which consists of beds of tine drab- 

 coloured sandy clay, having vegetable remains scattered through the 

 mass. These vegetable remains, when in such a condition that they 

 can be recognised, are, for the most part, fragments of Eqrtiseta. 

 The contents of this silty deposit are, however, not confined to such 

 organisms as ordinary swampy vegetation. On submitting portions 

 of the silt to microscopic examination this substance is found to 

 afford many species of Diatomacese, associated together in an inter- 

 esting manner. Professor Gregory states that the following forms 

 of Diatoms occur : — 



Epithemia IIjTidmanni. 

 Cymbella Seotica. 



maculata. 



Coscinodiscus radiatus. 

 Cyclotella operculata. 



Kutzingiana. 



Campylodiscus cribrosus (?). 

 Trj'blionella acuminata, 



punctata. 



marginata. 



Sum-ella minuta. 



nobilis (or biseriata ?). 



Navicula didyma. 



ovalis. 



rhomboides var {Gregory). 



varians {Gregory), 



Pinnularia major. 



viridis. 



acuta. 



tenuis {Gregory). 



Gomphouema tenelluni. 

 Doryphora amphiceros(tine). 

 Synedra radians. 

 Nitzschia (sp. ?). 

 Grammatophora marina. 

 Melosira sulcata. 



distans. 



Fragilaria virescens. 

 Odontidium mesodon. 

 Meridion circidare. 

 Achnautliidium lauceolatum . 



This association of marine and freshwater forms indicates the oc- 

 Ann. ^- Mag. N. Hist. Ser. 3. Vol. xvi. 10 



