TRANSACTIONS OF SECTION C. 717 



5. Thirteenth Report on the Circulation of Underground Waters. — See 

 Reports, p. 358. 



6. Notice du Dlnothei-ium, deux especes, trouvSes en Espagne. 

 By Professor Vilanota. 



7. On the Oenus Piloceras, Salter, as elucidated hy examples lately 

 discovered in North Amsricx and in Scotland} By Arthur H. Foord 

 F.G.S. 



The genus Piloceras was first described by Salter in 1859 from imperfect 

 specimens consisting only of wliat has since been proved to be the siphuncle of a 

 shell closely allied to Endoceras. 



E. Billings and Sir AVilliam Dawson in Canada, and R. P. AVhitfield in the 

 United States, have each described and figured species of Piloceras in which the 

 septa are preserved. Whitfield has recently ('Bull. Amer. JMus. Nat. Hist. New 

 York,' vol. i. No. 8, December 1886) described a species {Piloceras e.vplanafm-) in 

 which the body-chamber, septa, and fragments of the test are preserved, with the 

 siphuncle in place. 



A few years ago Mr. B. N. Peach, of the Geological Survey of Scotland, 

 discovered in the Durness limestone, Sutherlandshire (whence Salter's orin-inal 

 specimens were obtained) examples of Piloceras in which the septa and siphuncle 

 are seen in conjunction. 



These examples may most probably be referred to Piloceras invaginatum, Salter. 



From a geological point of view Piloceras is interesting from its occurrence in 

 rocks forming part of a series which is identical, in order of succession and appa- 

 rently in fossil contents, in North America and in Scotland. 



In an able address to the Koyal Physical Society of Edinburgh (1885) Mr. 

 Peach has pointed out that the Silurian strata of Sutherlandshire is represented in 

 Eastern North America by (1) the Potsdam sandstone, bored hj Scolithus,]\.\&t 

 like the 'pipe-rock' of Sutherlandshire ; (2) the Oalciferous Group'; (.3) part of the 

 Trenton Group. 



In consideration of this remarkable similarity between these two widely 

 separated areas, Mr. Peach concludes ' that some old shore-line or shallow sea 

 must have stretched across the North Atlantic or Arctic Ocean, along which the 

 forms migrated from one province to the other, and that some barrier must have 

 cut oif this area from that of Wales and Central Europe.' 



The genus Piloceras may now be thus re-defined : — 



Shell more or less broadly conical; slightly curved; somewhat compressed 

 laterally; elliptical in section. Septa rather numerous. Siphuncle formed bv the 

 prolongation and conjunction of the necks of the septa; marginal: very faro-e • 

 partaking of the curvature of the shell ; provided internally with one or more 

 conical, or funnel-shaped sheaths, which are united at the top with its mai-n-in. 

 These sheaths apparently communicated with one another by means of the einii)- 

 siphon, which perforates the apex of the siphuncle. The endosiphon orio-inated in 

 one of the earlier of the septal chambers, if not in the initial chamber itself. 



8. Beport on the Fossil Plants of the Tertiary and Secondary Beds of the 

 United Kingdom. — See Reports, p. 229. 



9. First Beport on the ' Manure ' Gravels of Wexford. — See Reports, p. 209. 

 ' Published in cxtenso in the Geol. 3Iag. new ser. dec. iii. vol. iv. December 1887. 



