Ch. XXYIL] 



LLAXDOYERY ROCKS. 



561 



oblongus, which, some zoologists consider as the young of P. Icevis, 

 others as a distinct species: both forms have a wide geographical 

 range, being also met with in the same part of the Silurian series in 

 Russia and the United States. 



Fig. 64L 



Pentamerus Icevis, Sow. "Upper and Lower Llandovery beds. 

 Perhaps the young of Pentamerus oblongus. 

 ff, 5. Views of the shell itself, from figures in Murchison's " Silurian System." 



e. Cast with portion of shell remaining, and with the hollow of the central septum filled 



-with spar. 

 d. Internal cast of a valve, the space once occupied by the septum being represented by a 

 hollow in which is seen a cast of the chamber within the septum. 



Fig. 642. 



The May-Hill or Upper Llandovery group sometimes consists of 

 a conglomerate, but oftener of limestones and shales, especially in the 

 upper part. It ranges from the skirts of the Longmynd by Builth, 

 Llandovery, and Llandeilo, to the sea in Harlow's Bay, where it is 

 particularly well exhibited in the cliffs. The conglomerate is derived 

 from the waste of the Lower Silurian rocks. About sixty species of 

 fossils are known in the May-Hill divis- 

 ion, more than half of which are, ac- 

 cording to Mr. Salter, Wenlock species. 

 They consist of trilobites of the genera 

 Illcenus and Calymene ; Brachiopods 

 of the genera Orthis, Atrypa, Leptcena, 

 Pentamerus, Strophomena, and others ; 

 Gasteropods of the genera Turbo, Mur- 

 ckisonia, and Bellerophon ; and Ptero- 

 pods of the genus Conularia. The 

 Brachiopods are almost all Upper Silu- 

 rian species. 



Among the fossils of the May-Hill 

 shelly sandstone at Malvern, Tentaculites annulatus (fig. 642) 



Tentaculites annulatus, Schlot 

 Interior casts in sandstone. 

 Upper Llandovery and Caradoc sand- 

 stone, Eastnor Park, near Malvern. 

 Nat size and magnified 



an 



annelid probably allied to Serpula, is found. It is also abundant in 

 the Caradoc or Lower Silurian. 



Llandovery Bocks (Lower Llandovery of Murchison). — Below the 

 May-Hill group are the Llandovery Rocks, so named from a town in 

 36 



