I2 4 



OUR COMMON BRITISH FOSSILS. 



imbedded in the Chalk, in the neighbourhood of 

 Norwich. 



Glyptocrinus basalts is common almost everywhere 

 in the Silurian rocks, but especially so in those of 

 Wales. At Mynydd Fronfrys, about two or three 



Fig. 106. Fossil Encrinites found in the Wenlock limestone (Silurian), i. Mar- 

 supiocrinites ceslatus ; 2, tase of arms of ditto (magnified); 3, proboscis of 

 ditto inserted in fossil shell of Acroculia haliotis ; 4, Crotalocrinus rugosus 

 (reduced in size) ; 5, pelvis of ditto (natural size) ; 6, flat stomach surface of 

 pelvis showing bases of the arms; 7, portion of the reticulated fingers of 4^, 

 showing their anchylosation. (After Symonds.) 



miles from Llangollen, large numbers of the remains 

 of this fossil may be found associated with those of 

 other common Silurian Crinoids. The generic name 

 of Glyptocrinus (signifying " sculptured ") is in allusion 

 to the highly ornamented basal plates of the body or 



