l82 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Prestwich have been fully realized, through the determination of 

 the Devonian and Silurian rocks in Middlesex and Hertfordshire, 

 immediately below the Cretaceous series. 



Echinodermata. — 7 genera of Crinoidea, 2 Asteroidea, and 1 

 Blastoid are all that are known of this class in the British Devo- 

 nians. 80 genera have been described from the Devonian rocks of 

 Europe and America. By comparison, therefore, the British fauna has 

 scarcely any claim to recognition, and 5 of the 7 Crinoidea are also 

 Carboniferous in Britain. It cannot be said, therefore, that the species 

 in this division of the order are representative in Britain. The 10 

 genera and 24 British species are of necessity unequally distributed. 

 Actinocrinus tenuistriatus, Phill., Cyathocrinus megastylus, Phill., 

 and C. pinnatus, Goldf., are the only forms known in the Lower 

 Devonian ; 6 genera and 12 species occur in the Middle Devonian, 

 viz. Actinocrinus 1 species, Cupressocrinus 2, Cyathocrinus 3, Hexa- 

 crinus 3, Platycrinus 2, and Taxocrinus 1 species. 



The Asteroidea all belong to the upper division, and are mostly 

 from the North-Devon beds, which with them have also yielded 7 

 Crinoidea. We have therefore 8 genera and 14 species in the Upper 

 Devonian beds of North Devon — Protester 2 species, Palceaster 2, 

 Helianihaster 1, Pentremites 1, Aclelocrinus 1, Actinocrinus 1, Cyatho- 

 crinus 5, and Taxocrinus 1 species. Of the whole fauna (24 species) 

 3 genera and 6 species pass to the Carboniferous ; they are Actino- 

 crinus triacontadactylus, Cyathocrinus ellipticus, C. geometricus, C. 

 pinnatus, C. variabilis, and Pentremites ovalis. Three of these are 

 European Devonian. 



Annelida. — Serpula advena, Salt., occurs in the Upper Old Red 

 Sandstone of Caldy Island, and Tentaculites annulatus?, Schloth., 

 in the Middle Devonian of North Devon ; the last named is abundant 

 (in places) in the limestones near Ilfracombe. 



Crustacea. — All the 4 orders, illustrated only by 20 genera and 

 37 species, are represented in the British Devonians ; 45 genera and 

 290 species, however, have been described from Bohemia, Germany, 

 Spain, Asia, Africa, America, &c. 20 of the foreign genera and 200 

 species are Trilobita ; the remaining 90 are Merostomata, Phyllopoda, 

 and Ostracoda. As in the case of the Echinodermata our Crustacean 

 fauna is anything but representative, yet it has a characteristic 

 facies that carries with it the conviction of distinctness. Only 6 

 genera of Trilobita are known, viz. Bronteus {flabellifer), Cheirurus 

 (articulatus), Harpes (macrocephalus), Homalonotus (elongatus) y Pha- 

 cops (5 species including the subgenera Tr inter ocepJialus and Cryphceus), 

 and Phillipsia (Brongniarti) ; the doubtful genera have been relegated 

 to their supposed places. 9 genera and 24 species of all the orders 

 are Lower Devonian (6 genera are Trilobita), 5 genera and 6 species 

 are Middle, and 7 genera and 9 species are Upper Devonian. 

 Eurypterus (6 species), Stylonurus (6 species), and Ptcrygotus (4 

 species) are all, with one or two exceptions, Lower Old Red Sand- 

 stone types. None of these are known to occur in the typical Devonian 

 area, being either Scotch or in the Silurian region. The singular 

 genus Prcearcturus (P. gigas, Woodw.) of the family Idoteidae is 



