150 



MESSRS. KIRKBY AND DUFF ON THE 



Figs. 19-29. Spicules from suckers of Thyone fusus, x 200. 

 Figs. 30-39. „ „ body of the same, X 200. 



Fig. 40. Plate from sucker tip of the same, X 200. 



PLATE III. 



Spicules from foot of mature Psolus phantapus, x 200. 

 Part of plate from sucker tip of the same, x 200. 

 Spicules from foot of immature, the same, x 200. 



,, ,, body of Thyone rapkanus, x 200. 



,, (plates) from sucker tips of the same, x 200. 



PLATE V. 



Echinocardium peiinatifidum, nat. size. 



Valves of pedicellarife from ditto, x 50. 



Left anterior lateral pores of E. pennatifidum, nat. size. 



,, ,, E. cor datum, nat. size. 



,, ,, E. ovatiun, nat. size. 



JlgS. 



Fig. 



l-n. 

 12. 



Figs. 



13-21. 



Figs. 



22-28. 



Figs. 



29-30. 



Fig. 



1. 



Figs. 



2-4. 



Fig. 



5. 



Fig. 



6. 



Fig. 



7. 



IV. — Notes on the Geology of Part of South Durham. By Jas. 



W. KlRKJBY AND JOSEPH DtTFF. 



The following observations are properly termed notes on the geo- 

 logy of the district of which they treat, the said district being 

 the country about the village of Etherley. They are notes in 

 the sense of their making no claim to being a full account of the 

 geology of that region, being rather the results of such researches 

 as circumstances or disposition occasionally permitted or suited 

 the authors to make (often in company) during the years 1866, 

 1867, and 1868. 



The prevailing rocks about Etherley are Coal Measures be- 

 longing to the lower portion of the series. To the north and 

 north-east these are the only rocks present. A few miles west- 

 ward they outcrop and give place to the Millstone Grit, which 

 forms much of the fell land in the west of the county. Within 

 as short a distance to the south the coal-field also terminates by 

 the rather abrupt outcrop of its beds, the grit again occupying 



