MOLLUSCA (except CEPHALOPODA). 139 



(Fig. 74 a), which had a very wide distribution during this 

 Age (Ouralian). Marine forms are Aviculopecten papyraceits, 

 Pinna costata, and Numlana attemmta from Scotland. 

 Among lamellibranchs from the Mountain Limestone are the 

 peculiarly shaped Conocai'dium and various species of Cardio- 

 nioiyha. Posidonomya Beclieri is widely distributed in the 

 Lower and Middle Carboniferous, often occurring in abundance 

 and giving its name to certain beds in this country and on 

 the Continent (Fig. 74 h). The gastropods of Lower Carboni- 



Gallery 

 VIII. 



Fig. 74. — Carboniferous Lamellibranchs. a, Garhonicola {^Anthraeosial 

 robusta, Upper Coal Measures ; § natural size, b, Posidonomya Becheri, 

 Middle Carboniferous, North I)'evon ; natural size. (Table-case 15.) 



ferous age contain many genera not hitherto noticed ; among 

 these MacTOcheilns, the loose-coiled Phanerotinus, PJuomphalus, 

 and the wide-mouthed Bellerophon are conspicuous ; a large 

 shell of Naticopsis retains the operculum, lofty-spired forms 

 are represented only by Murcliisonict and Loxonema ; 3fo2tr- 

 lonia is a fore-runner of Pleurotomaria ; Platyceras {Capnlus\ 

 often occurs on the ventral surface of crinoids, living on 

 the food-particles that they reject. 



Devonian. During this epoch the sea existed where now 

 are found fossils similar to those found in the Devonian 

 limestones and slates of the Continent. The rocks that were 

 at the same time being deposited over the rest of the British 

 area are for the most part known as Old Eed Sandstone, and 

 seem to have been formed in lakes or estuaries. Evidence 

 of this is furnished by the large shells related to the modern Table-ease 

 fresh-water mussel, and called Archanodon Jnkcsi. Specimens ;Between 

 of this, the oldest non-marine lamellibranch as yet known, Wall-cases 

 come from rocks of Upper Devonian age in Northumberland, 7 & 8. 

 Monmouth, and Kiltorcan in S. Ireland. The marine forms Tablegcase 

 from the south-west of England are mostly Middle Devonian 

 gastropods from the collections of the late W. Vicary and 



