230 



Murchisoris Silurian System. 



where the beds are much disturbed by trap rocks, rich and 

 productive lead veins are found. 



The following is a general list of the fossils of the lower 

 Silurian rocks : — 



Area Eastnori, 

 Avicula orbicularis, 

 — — obliqua, 

 Atrypa (Spirifer) crassa, 



1 — undulata, 



— lens, 



plana, 



globosa, 



polygramma, 



— orbicularis, 



— — — hemispherica, 

 — affinis, 



Bellerophon trilobatus, 



- — __— acutus, 



• — — bilobatus, 



Bucinum(?) fusiforme, 



Euomphalus tenuistriatus, 



— perturbatus, 



corudensis, 



funatus, 



Lingula attenuata, 



Leptaena* (Producta) sericea, 



complanatus, 



duplicata, 



englypha, 



* Atrypa, Leptaena, and Orthis, are subdivisions of the great genus 

 Terebratula. Leptaena are distinguished in little from the genus Pro- 

 ducta. Atrypa are Spirifers, with a short hinge, and destitue of for- 

 amen, or having a small triangular one ; and with acute, not perforated 

 beaks. 



Orthis is distinguished from Spirifer, by its long narrow hinge and 

 circular flat striated shell. — Ed. 



