140 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



land, although, considering the somewhat abundant forms in Shrop- 

 shire (9) and Scotland (11), and that the Westmoreland area inter- 

 venes, we might expect some to occur. The genus Euomphalus in 

 Ireland (with 7 species), Holopcea in Merioneth (7), Murchisonia and 

 Rhaphistoma in North Wales generally (12), constitute nearly one 

 half the univalve fauna — Trochonema, Turbo ?, Trochus ?, and Pleu- 

 rotomaria having but few species in each. 8 genera and 19 species 

 actually pass up to the succeeding Llandovery, Wenlock, and Ludlow 

 rocks above. The Lower Llandovery receives 10 species, and the 

 Upper 16 ; the W^oolhope 1 (Turbo tritorquatus, M'Coy), the Wen- 

 lock 2 (Euomphalus alatus, His., and E. sculptus, Sow.). 3 species 

 range into the Ludlow — Euomphalus alatus, Holopella cancellata, and 

 H. conica. Three species of Gasteropoda are common to the Llan- 

 deilo below — Cyclonema crebristria, Murchisonia simplex, and Turbo 

 tritorquatus. The relationship of the two Llandoveries is marked ; 

 the Lower has 103 species of all classes in common and the Upper 

 107, Ireland and Scotland possessing the highest numbers, being re- 

 spectively 304 and 206. 



Pteeopoda. — Ten species of this class occur, the largest pelagic 

 Pteropod fauna known in the Palaeozoic rocks ; they occur in nearly 

 equal numbers through the 10 areas, Ireland still yielding the 

 highest number, nearly three times as many as Shropshire and 

 Merioneth. No species is known in Pembrokeshire. 



Hetekopoda. — This order is represented in the Caradoc and Bala 

 rocks by 11 species of Bellerophon, 2 of Ecculiomphalus, and 3 species 

 of Maclurea. In the British area the two last-named genera are 

 restricted in their geographical range to Ireland and Scotland, and 

 stratigraphically to the Arenig or Llandeilo and Caradoc. Maclurea 

 is known only in Scotland ; M. Logani, Salt., M. Peachii, Salt., 

 M. macromphala, M'Coy, and M. magna are said to be (in Scotland) 

 of Llandeilo age. The Durness species, M. Logani and M. Peachii, 

 with their associated forms, I believe to be Arenig. Piloceras in- 

 vaginatum and Orthoceras menclax occur in the same beds. Maclurea 

 abounds in the Chazy Limestone of the United States and Canada 

 — beds probably to be correlated with our Lowest Llandeilo, the 

 Upper Cambrian or Lower Bala group of Sedgwick. M. M-Goyi, 

 M. macromphala, and M. magna are admitted to be with us of 

 Caradoc age, and certainly occur low down in the series. Clonmel, 

 Stinchar river and Bugon &c. in Ayrshire, and the Durness Lime- 

 stones yield M. Peachii and M. Logani abundantly. 



I have preferred to place Ecculiomphalus with the Heteropoda 

 rather than the Pteropoda, although Portlock's genus may be one 

 of the latter group. 



Cephalopoda. — No less than 47 species have been determined 

 from the Caradoc series ; their maximum development is in Ireland, 

 where 6 genera and 24 species occur ; no species is known in Shrop- 

 shire. Westmoreland and Scotland register 12 each. The Irish 

 genera are Cyrtoceras, Koleoceras, Lituites, Poterioceras, Trocholites, 

 and Orthoceras. As a generic fauna this is by far the largest in 



