466 Geological Society. 



segments. The surface of the caudal plate is also divided longi- 

 tudinally by two depressions into three broad subtriangular lobes. 



Prof. Huxley described in detail the process of his determination 

 of the above-described characters from the successive examination of 

 the several specimens ; and intimated that at first, so problematical 

 were the characters afforded by one or two specimens only, that the 

 broader extremity was regarded as possibly the cephalic buckler of an 

 anomalous Apus-like crustacean, with its dorsal surface presented to 

 view. Subsequent examination of the specimens kindly lent by 

 Mr. Cooper enabled the author to take a. different and more probable 

 view of the structural relations of these interesting fossils. Mr. 

 Huxley pointed out that the Pygocephalus Cooperi has some peculiar 

 relations with the little Mysis or Opossum-shrimp, especially in the 

 schizopodous character of its thoracic appendages, in the proportional 

 size of the carapace, and in the gradual increase in width, from 

 before backwards, of the sterna of the thoracic somites. In the 

 proportions of its abdomen, however, the Py(/ocej:>//a/«s approximates 

 more nearly to the true Stomapoda ; and a Gonodactylus bent upon 

 itself presents an appearance in some respects very analogous to that 

 of the fossils in question. 



3. " On the Geology of Strath, Isle of Skye." By A. Geikie, 

 Esq. Communicated by Prof. Ramsay, F.G.S. 



In his introduction the author referred to Prof. Jameson's mine- 

 ralogical observations on this district, to Dr. MaccuUoch's subsequent 

 and more extensive descriptions, and to Sir R. Murchison's further 

 account of the stratified rocks of the eastern coast of Skye. The 

 character and sequence of the liassic beds of Strath were then detailed ; 

 the author pointing out some instances in which his recent observa- 

 tions do not bear out Dr. MaccuUoch's account of the geology of this 

 part of Skye. Mr. Geikie enumerates the following liassic beds, as 

 occurring in Strath : — 1. (lowest, and resting on the red sandstone 

 and quartzite of Sleat) a fine conglomerate, 2 to 3 feet thick, seen 

 at Heast; 2. green and yellow sandstone, 3 to 15 feet; 3. Hmestone, 

 1 foot: coral-bed (with Isastraa), 2 feet ; 4. calcareous grit, 7 to 8 

 feet; 5. limestone with occasional seams of shale: Nos. 4 and 5 

 contain Ammonites, Gryphcea, and Pentacrinites : Nos. 2 to 5 are seen 

 at Lussay ; 6. white sandstone ; 7. dark brownish-grey sandy shale ; 



8. calcareous brecciated conglomerate, seen at Obe Breakish ; 



9. limestones and shales in alternate bands (Broadford); 10. calca- 

 reous grits with Gryphaee, seen at Corry : Nos. 1 to 10 are referred 

 to the Lower Lias ; 11. dark grey or brown sandy micaceous shales 

 (Pabba), with numerous fossils; and 12. dark calcareous shales 

 (Scalpa), with Pecten, Osiraa, &c. : Nos. 11 and 12 are referred to 

 the Middle Lias. The dip of these beds along the author's section 

 from their base at Lussay to their top at Scalpa House is N.W. at 

 an angle of 5° to 8° ; and he estimates their thickness at about 1500 

 feet. Taken as a whole, the liassic beds of Strath appear to form 

 a great synclinal trough, striking N.W. to S.E., bounded by syenite 

 and red sandstone, and ridged up along its centre by an anticlinal 

 axis. Mr. Geikie, in describing the several exposures of the beds 



