i3 6 



PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



^ , , f Shropshire has yielded 15 genera and 31 species. 



Jin ^ ana ' \ Westmoreland „ 18 „ 38 „ 



Scotland „ 31 „ 78 „ 



Ireland „ 31 „ 90 „ 



The most important genera, or those of chief stratigraphical value 

 and in which the species are numerous, are Acidaspis (8 species), 

 Ampyx (6), Agnostics (5), Asaphus (6), Calymene (8), Cheirurus (6), 

 Homalonotus (4), lllcenus (13), Lichas 6, Phacops (13), and Remo- 

 pleurides (8). The genera essentially characterizing the Caradoc are 

 Harpes, Salteria, Remopleurides, Cyclopyge, Dionide, Tiresias, and 

 Cyphoniscus, most of which are only represented by one or few 

 forms. Scotland and Ireland possess the richest assemblage of species ; 

 26 genera and 63 species occur in the former, and 23 genera and 

 77 species in the latter area. Only 15 of the 123 species of Trilo- 

 bita pass to the Lower Llandovery ; they are Acidaspis Brightii, 

 Calymene Blumenbachii, C. brevicapitata, C. caractaci, C. Allportiana, 

 Cheirurus bimucronatus, C. clavifrons, Encrinurus punctatus, Cy- 

 phaspis megalops, Cybele verrucosa, Illcenus Bosenbergii, I. Bowmanni, 

 I. Thomsoni, Lichas laxatus, and Phacops Brongniarti. 8 of 

 these same also pass up into the Upper Llandovery, 6 to the 

 Wenlock, and 5 to the Ludlow. The long-ranged species are 

 chiefly those illustrating the largest genera, such as Calymene 

 Blumenbachii, C. Allportiana, Cheirurus bimucronatus, Encrinurus 

 punctatus, Cyphaspis megalops, and Phacops caudatus, all of which 

 species appear in the Ludlow and then cease to exist, the Devo- 

 nian rocks having none in common ; yet Bronteus and Harpes are 

 repeated from the Caradoc in the Middle Devonian, both in Britain 

 and on the continent. We must remember, however, that the 

 marine Devonian nowhere visibly overlies the Silurian rocks in Great 

 Britain, and the Old Eed Sandstone contains no true marine form 

 anywhere. 



The order Ostracoda, illustrated by Beyrichia, Leperditia, Cythere, 

 Primitia, and Entomis, needs little more than notice here ; they 

 have received at the hands of Professor Rupert Jones the closest 

 scrutiny both zoologically, palaeontologically, and stratigraphically ; 

 few men have so largely added to our knowledge of the orders 

 Ostracoda and Phyllopoda. 



Brachiopoda. — And next to the Crustacea in force and classifica- 

 tory value we must place this group of Mollusca or Molluscoida. 

 Numerically in the whole of the Cambrian and Silurian rocks the 

 Crustacea include the largest number of species, 550 being known ; 

 whilst of the Brachiopoda we know 456. Individually no class sur- 

 passes the Brachiopoda through all the Palaeozoic and Mesozoic rocks, 

 many genera being, however, far more richly represented than others. 

 In the Caradoc this is notably the case. The genus Orthis has in 

 Britain alone, we know, through the large collections that have been 

 made and the elaborate researches of Davidson, no less than 110 

 species, and culminates in the Caradoc. In tracing the numerical 

 and stratigraphical value of the genus, we And that in the Cambrian 



