190 Proceedings of the Royal Physical Society. 



longer and expanded at one end; those only which have 

 attained their full length begin to develop flukes ; and it is 

 not until the anchors are completely grown that we detect 

 any trace of the anchor-plates." * 



The same authors describe a corresponding development 

 in the wheels of Myriotrochus. These " first appear as little 

 stars, with rays or spokes of variable number, which increase 

 until they attain their normal length, and then expand at 

 their ends, until they join and form a rim (or tire) to the 

 wheel." t 



3. The Plates and Spicules from the Carboniferous Limestone 

 Scries of Scotland. — As before stated, remains which we con- 

 sidered referable to this group first came under the notice of 

 Mr Bennie and myself in 1873, from the localities named, 

 but in small numbers. Since then Mr Bennie has met with 

 these plates and spicules in quantity at two localities in the 

 East of Scotland — at Woodend Quarry, near Fordel, Fife; 

 and in a section on the river Avon at Kinneil Mill, near 

 Linlithoow. The fossiliferous shale at Woodend is above the 

 limestone, the latter being the No. 2 Limestone of the Lower 

 Carboniferous Limestone Group ( = Hosie Limestone of Lanark- 

 shire). The stratum yielding the remains at Kinneil Mill is, 

 Mr Bennie believes, the shale above the Dykeneuk Lime- 

 stone ( = Gair Limestone of West of Scotland) of the Upper 

 Carboniferous Limestone Group. 



The microscopic organisms may be described as follows : 



a. Perforated Plates of various sizes. — By far the commonest 

 forms are irregularly rounded and slightly convex plates, with 

 a diameter varying from -^Qih. to -J^^th of an inch. When 

 perfect, the marginal outline is undulating, but as a rule the 

 plates are imperfect and broken. Each plate is pierced by a 

 variable number of perforations giving to the entire organism 

 the appearance of a network with the finest possible mesh. 

 The perforations are circular or oval, vary in size in the same 

 plates, and have entire edges. They are usually largest in 

 the centre, and decrease towards the margins of the plate, or 

 sometimes towards one end, although neither of these rules 

 always holds good. They vary in size from "005 downwards. 



* Annals Kat. Hist, 1859, iii., p. 217. + Ihid., p. 220. 



