363 Proceedings of the Royal Physical Society. 



knowing where to place these organisms. Many of them 

 are certainly not Pteropods. Some are more probably 

 worms, and some of those with lids, such as Ryolithus, may 

 even be extreme forms of hingeless Brachiopods. Two other 

 species of Salterella, besides the well-known S. Maccullochii, 

 Salter, occur in the Durness Limestone, while several species 

 of Hyolithus have been found along with Olenellus in the 

 Fucoid beds in several localities in the north-west High- 

 lands. Mrs Gray records several species of Hyolithus from 

 the Silurian rocks of Girvan.i 



CEPHALOPODA. 



The chief work among Scottish Palaeozoic Cephalopoda 

 has been in the classification of old material. The Eev. J. 

 P. Blake, in his Monograph published in 1882,2 describes, 

 from the Gray collection of Silurian Cephalopods from the 

 Girvan region, one new species of each of the following 

 genera: — Orthoceras, Cyrtoceras, Siud Gomphocer as; and three 

 new species of Orthoceras from the Silurian rocks for the 

 Geological Survey collection. Of Cambrian forms from the 

 Durness Limestone, he adopts the Orthoceras meiidax, Salter, 

 and makes two species — 0. durinum and 0. pertinens. He 

 looks on Piloceras as a genus not sufficiently established. 

 H. H. Foord makes use of Scottish material for his British 

 Museum Catalogue published in 1888.^ He accepts the 

 Piloceras invaginatum of Salter, and shows, from specimens 

 belonging to the Geological Survey of Scotland, obtained 

 during the progress of the Geological Survey in Durness in 

 1881-82, the relation of the siphuncle to the septa and body- 

 walls, as well as the arrangement of the invaginating sheaths 

 of the siphuncle. He considers the Orthoceras mendax, 

 Salter, from peculiarities of the siphuncle, to belong to the 

 genus Actinoceras. In the Geological collection from the 

 Durness Limestone, as well as the siphuncles of several 



1 Me7n. Geol Sitr., "The Silurian Rocks of Britain," vol. i. pp. 686-697, 

 1900. 



'^ "Mon. of Brit. Foss. Ceph.," part i., 1882. 



8 " Cat. of the Foss. Ceph. in the Brit. Mus.," part i., 1888 ; part ii., 1891 ; 

 part iii.^ Foord and Craik, 1897. 



