946 



NEW YORK STATE MUSEUM 



a relatively rich lamellibranch fauna. In regard to these, 

 Brogger disagrees with Hicks's view of considering their fauna as 

 closely allied to the Lingula flags, but holds that the species of 

 Neseuretus and the lamellibranch fauna point to a younger age 

 and indicate a shallow water facies of the deeper water deposits 

 of the Tremadoc of north Wales, with which he correlates these 

 beds. The latter would, then, also have to be transferred to 

 the Lower Siluric. They are also underlain by the Dictyonema 

 slates; which accordingly would also in Wales denote the upper 

 boundary of the Cambric, instead of falling within the Cambric 

 as held by Salter, Callaway and Hicks. 



Freeh shares the views of the Scandinavian geologists as to 

 the parallelization of the Scandinavian and British Cambrian- 

 Silurian beds and holds with Brogger, that, though the relations 

 of the English Tremadoc to the Cambric are more distinct than 

 those of the Ceratopyge limestone to the Cambric on account 

 of the prevalence of the Olenidae and Lingulellae, this fact is 

 not of conclusive importance, as the Tremadoc is characterized, 

 like the Ceratopyge limestone, by the appearance of those tri- 

 lobite families which reach their principal development in the 

 Lower Siluric. The Asaphidae, Lichadae and Ampycidae appear 

 immediately above the Dictyonema slate; the Cheiruridae and 

 Trinucleidae occur already in numerous representatives in the, 

 Upper Tremadoc; while the Olenidae and Conocephalidae of 

 the Cambric are represented only by genera, not pertaining to 

 the Cambric proper, as Ceratopyge, Euloma, Remopleurides, etc. 

 Freeh concludes that no doubt can be entertained as to the 

 Lower Siluric position of the Tremadoc terrane and adds that 

 the confusion existing in England in regard to the boundary of 

 Cambric and Siluric excludes a solution of the problem by recog- 

 nizing the rights of historic priority. 



Professor Kayser also, in his Geol. Formationskunde, which 

 has just appeared in a new edition (1902, p.48), holds that the 

 Dictyonema bed forms the top of the Lingula shale and not the 

 base of the Tremadoc shale, as the English geologists maintain, 

 and further that the Tremadoc is a part of the Siluric formation; 

 that hence, also in England, the Dictyograptus bed closes the 

 Cambric formation. 



