and the JVeiv Genus Protistograptus. 53 



Graptolitoidea 



Dictyonema delicatatum Dawson var. 

 D. quadrangulare Hall 

 Clonograptus flexilis (Hall) 

 Didymograptus indent us (Hall) 

 JRetiograptus tentaculatus Hall? 



Brachiopoda 



Orthis orthambonites Pander 



O.f euryone Billings 



O. (Dalmanella ?) electro, var. major Matthew . 



0. electra var. Imvis Matthew 



0. menapiw var. aeadica Matthew 



Pteropoda 



Styliola primaiva Matthew 

 Cephalopoda 



Orthoceras cf. priamus Billings 



O. cf. catulus Billings 

 Trilobita 



Parabolinella posthuma Matthew 



Cyclognathus rotundlfrons Matthew 



Euloma sp.? 



Stratigraphy and Correlation. — Matthew (1892J) and Ami 

 described the fauna of the Tetragraptus zone in 1892 and 

 correlated it with the Arenig of England. Later, Ruedemann 

 (1904), on the basis of Matthew's publications, correlated it 

 with the Tetragraptus zone (Beds 1 and 2) of the Deepkill, the 

 main Point Levis zone, and the Dichograptus zone of the 

 Middle Skiddaw slates of the Lake Disti'ict, England. 



A considerable advance has been made in the study of 

 graptolites since 1892. New species have been recognized and 

 the successive zones have been worked out in greater detail. 

 A reexamination of the fauna, in the light of the new data, is 

 therefore desirable in order to modernize the species and to fix 

 the age as accurately as possible. 



The fossils of horizon A are those of the Tetragraptus zone. 

 Didymograptus simulans, which, according to Ruedemann, is 

 not present in the Deepkill locality, links the fauna with that 

 of the Middle Skiddaw slates of the Lake District. Elles (1898) 

 subdivides this formation into (1) Upper Tetragraptus zone, (2) 

 Dichograptus zone, and (3) Lower Tetragraptus zone. Local 

 faunal lists are not given by Miss Elles, so that it is not easy to 

 correlate accurately with these zones. Ruedemann, however, 

 regards the Dichograptus zone as the equivalent of the 

 Tetragraptus bed of the Deepkill. It is probable, therefore, 

 that Bed A is to be compared with this zone in the Lake 

 District. 



