178 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 20, 



The characteristic fossils of the Bala limestone and slates have now 

 been often quoted. Those in the limestone itself are ordinarily 

 distinct from those found in the more sandy strata above and below ; 

 but in the more earthy parts of the limestone this distinction is lost : 

 the following may be considered quite characteristic of the group : — 



Fossils of the sandstones and ash- 

 beds. 



Trimicleus concentricus.* 

 lUsenus Bowmanni. 

 Asaphus Powisii.* 

 Phacops apiculatus.* 



conophthalmvis. 



Calymene brevicapitata.* 

 Lichas laxatus. 



Fossils of the Bala limestones. 

 Crustacea. 



Trinucleus seticornis.* 

 Illgenus Davisii. • 

 Cj'bele rugosa. 

 Encrinurus sexcostatus. 

 Phacops alifrons, rare. 

 Calymene Blumenbachii, rare. 

 Lichas laxatus.* 

 Cheirurus bimucroiiatus.* 



octolobatus. 



clavifrons. 



Ampyx tumidus.* 

 Agnostus trinodus. 

 Remopleurides radians. 

 Cythere, 2 small species. 



MOLLUSCA. 



Oncoeeras, 2 or 3 species. 

 Lituites comu-arietis. 

 Holopea, 2 or 3 species. 

 Miirchisonia scalaris. 

 Orthis biforata.** 



Vespertilio.* 



calligramma (plicata, Sil. 



Syst.).* 

 ■ Actonise.* 



elegantula.* 



Leptaena sericea.* 



tenuicincta. 



quinquecostata. 



Strophomena tenuistriata.* 

 Crania divaricata. 



Radiata. 



Cystideaj — several species.* 

 Encrinite stems, abundant. 

 Stenopora fibrosa.* 

 Retepora Hisingeri. 

 Ptilodictya fucoides. 



The same fossils are repeated, species for species, on the opposite 

 or eastern side of the trough of Caradoc sandstone, at Llanlyllin, 

 Llanwyddyn, Meifod, &c.; and the calcareous bands S. of Llangollen 

 present the same assemblage, with some trifling variations, and with 

 a larger proportion of corals. 



The fossils of the Hirnant or Upper Bala limestone have been enu- 

 * The abundant species are indicated by asterisks. 



Beyrichia complicata.* 



Turbo crebristria.* 

 Murchisonia scalaris.* 

 Orthis biforata.* 



Vespertilio.* 



calhgramma (plicata).* 



flabellulum.* 



elegantula.* 



Leptaena sericea.* 



Strophomena depressa. 

 orthisoides. 



Glyptocrinus basalis.* 

 Stenopora fibrosa.* 

 Retepora Hisingeri. 

 Petraia subduplicata. 



