176 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



rhomboidalis, and Lingula cornea. The last named in the Ludlow 

 country passes into the lowest beds of the Old Red Sandstone. The 

 others named are " Devonian " of the Worth and South Devonshire 

 areas, and not known in the Old Red proper. In the Passage-beds 

 into the Old Red of Herefordshire, Shropshire, and Worcestershire 

 some 5 or 6 species occur ; they are Chonetes striatellus (latus), Dis- 

 tinct rugata, Lingula cornea, Lingula minima, and Strophomena 

 rhomboidalis. They are associated in places with a few Asiphonida 

 of shallow-water habits, Pterincea, Modiolopsis, Ortlionota, &c. The 

 Lower Ludlow has yielded 13 genera and 38 species, 33 of which 

 are Wenlock. 12 genera and 25 species occur in the Aymestry 

 Limestone, and 11 genera and 24 species in the Upper Ludlow ; but 

 no genus is peculiar to either the Aymestry or Upper Ludlow beds, 

 the whole being represented in the Lower zone. 



The only species in the Ludlow not Wenlock are Lingula cornea, 

 L. lata, Orthis canaliculata, O.lunata, Rhynclwnella pentlandica, and 

 Strophomena ornatella. In other words, only these 6 species of 

 Brachiopoda are really Ludlow forms. Wo species is known in 

 Worth Wales, but 28 have been collected in South Wales. Here- 

 fordshire, Worcestershire, Shropshire, and Scotland have each yielded 



11 genera, and respectively 23, 27, 30, and 15 species ; Westmore- 

 land has 8 genera and 14 species ; Ireland 9 genera and 18 species. 



Lamellibranchiata. — Both the Lower and Upper Ludlow pos- 

 sess a large Molluscan fauna ; the Lower 14 genera and 34 species, 

 and the Upper 15 genera and 56 species ; the intermediate Ay- 

 mestry Limestone only 4 genera and 7 species — Pterincea Mans, 

 P. retrojiecca, P. Sowerbyi, Cardiola striata, Grammysia cingulata, 

 Ortlionota rotundata, and 0. semisidcata. The chief genera are Pte- 

 rincea with 12 species, Anodontopsis 7, Ortlionota 16, Modiolopsis 5, 

 Ctenodonta 4, Cucullcea 4, and Grammysia 4 species. The Passage- 

 beds contain 9 genera and 19 species, yet no single species occurs in 

 the Lower Old Red Sandstone ; with the change of lithological 

 characters all life seems to cease also, or no record is left. For the 

 life-history of those rocks, equivalent in time to those of the Old Red 

 Sandstone in the classical Silurian area, we have to consult the De- 

 vonian series of North and South Devon and Cornwall, where a 

 fauna unsurpassed in perfection, if not in magnitude, in all the in- 

 vertebrate classes exists — a group made famous in British geological 

 history through the labours and researches of Sedgwick, Murchison, 

 De La Beche, and Phillips. Westmoreland and Cumberland, through 

 the researches of Sedgwick and M'Coy, Harkness and Nicholson, in 

 the Kendal area, exhibit a large Ludlow Lamellibranchiate fauna ; 



12 genera and 37 species are known. Shropshire has 9 genera and 

 16 species, Worcestershire 8 genera and 17 species, Herefordshire 6 

 genera and 12 species, Scotland 6 genera and 13 species, and Ireland 

 only 2 genera and 3 species. North Wales hitherto has yielded only 

 1 genus and 4 species ; 13 genera and 21 species ranged from the 

 Wenlock into the Ludlow, thus altering the numerical value of the 

 Ludlow bivalves proper to 50 species, none of which passed the 

 Passage-beds between the Upper Ludlow and Old Red Sandstone. 



