646 PROFESSOR A. C. SEWARD ON 



1. White sandstones with bands of dark shaly carbonaceous sand: Cidaris 

 florigemma Phill., Hemicidaris intermedia Flem., Rhynchonella pinguis 

 Roem., Trigonia cf. T. hemispherica Lye. 

 The fossils obtained from Sput Dubh, mostly by Marcus Gunn, fix the Corallian age 

 of the strata No. 1 ; .and with them No. 2 may probably be included. The strata Nos. '6, 

 4, and 5 may be assigned to the Kimeridgian, and it is possible that in No. 6 there may 

 be representatives of Portlandian. The richer plant-beds No. 4 were discovered by 

 Marcus Gunn at Sron Rudha na Gaoithe, at the northern end of Culgower Bay. Else- 

 where in the bay the strata consist probably of dark shales, but they are hidden by 

 beach-sand and boulders. The old cliff-line, moreover, from Wester Garty to Loth 

 is mostly obscured, though the presence of shaly beds along the base may be inferred 

 from the springs and rushy ground, 



" The evidence seems to justify the following conclusions. The shales and sandstones 

 were deposited in an estuary or bay having features somewhat similar to those of the 

 Moray Firth at the present day. High cliffs of Old Red Sandstone (flags, etc.) bordered 

 the coast, and from these were formed screes, the material of which now and again 

 slipped into the waters and was partially rolled ; while huge blocks of flagstone occasion- 

 ally broke away and fell among the sediments, producing much disturbance. Even 

 layers were again deposited over the disturbed beds. In course of time widespread 

 earth-movements took place, whereby fissures were produced in the sediments already 

 to some extent consolidated, and these were filled from above by succeeding deposits, or 

 possibly to some extent from below, if the fissures were due to earthquakes. Evidence 

 of contemporaneous erosion also indicates local upheaval. Long subsequently the main 

 faulting was produced whereby the Jurassic rocks bordering the Old Red Sandstone and 

 granite were much crushed and broken, and numerous subsidiary faults were produced. 

 Hence we find complex structures, in part due to original irregularities of bedding and 

 to disturbance that led to the formation of pseudo-dykes, the mass of Jurassic strata 

 being afterwards broken and faulted in places by the later movements." 



In support of the Upper Oolite age of the strata between the Loth river and Helmsdale 

 a long list of fossils is given by Professor Judd # in his paper on this district. Three 

 species of shells associated with Culgower plants, which I sent to the British Museum, 

 were identified by Mr Newton and Mr Crick as Avicula sedilignensis Blake, Lima 

 concentrica Sow., and Amceboceras {Ammonites) alternans von Bueh, all Kimeridgian 

 species. 



In an appendix to Murchison's paper on the Brora coal-field, published in 1829, 

 K6NIG t described an Equisetaceous stem as Oncylogonatum carbonarium, and some other 

 plant impressions as "subtriangular carbonaceous plates." The Equisetaceous casts, as 

 Nicol and Hugh Miller \ believed, are no doubt identical with the well-known species 



* Judd (73), p. 182 ; see also Davidson (73), p. 196. t Konig, in Murchison (29), PI. xxxiii. 



| Miller (57), p. 468 ; (59), p. 142. 



