486 Mr. W. W. Stoddart on a Microzoal Bed 



Wyville Thomson (New Edinb. Phil. Journal, new series, 1861, 

 pis. 3, 4), which he calls Echinocystites, and considers to be a 

 a passage-form from the Cystidem towards the Echinida proper. I 

 do not see why they may not be rather a passage-form from the 

 Star-fishes to the Echinida ; for Agelacrinites and Edrioaster were 

 shown by Mr. E.Billings to be inflated star-fishes; and Paleodiscus, 

 which Prof. Thomson admits to be allied to his new genus, has 

 both a flattened form and transverse ambulacral ossicles with 

 grooves between them. The position of the anus, near to the 

 apical pole, as in many Asteriadce, the higher development of the 

 masticatory apparatus, and the thick clothing of the surface with 

 spines might all receive explanation readily if this curious form 

 were considered as a globular Star-fish, passing, by many of its 

 characters (the perforated ambulacral plates especially), towards 

 the Echinida. 



I am, your obedient Servant, 



J. W. Salter. 



EXPLANATION OF PLATE XVIII. 



Fig. 9. Protaster Miltoni, with magnified madreporic plate ; from Leint- 



wardine, Shropshire, in Lower Ludlow rock. 

 Fig. 10. Arm, under side : a, proximal end. The large passages for the 



feet are covered with a light tint. 

 Fig. 11. Ambulacral ossicles, magnified. 



XLIX. — On a Microzoal Bed in the Carboniferous Limestone of 

 Clifton, near Bristol. By W. W. Stoddart. 

 [Plate XVIII. figs. 1-8.] 

 The bed of limestone now to be described is, without exception, 

 the most extraordinary and interesting that it has ever been the 

 author's lot to examine. Numerous as are the small shells and 

 fossils in many of the Tertiary beds of the Isle of Wight, Hamp- 

 shire, and other places, yet they are all very far surpassed by the 

 immense number of organisms in the Clifton bed ; and so minute 

 are these, that it is a rare occurrence to find one the eighth of an 

 inch in diameter. The casts are so exquisitely perfect, that the 

 cell-aperture of the zoophyte or the hinge-markings of the Ento- 

 mostracan are frequently to be met with in a very good state of 

 preservation. 



The extensive section of the Carboniferous Limestone displayed 

 at Clifton has for a long period been well known and frequently 

 described by various geologists. The facility with which all its 

 different beds may be reached has always afforded good oppor- 

 tunities for their study. 



The section may be completely followed from the Upper De- 



