New Horizon in St. John Group. 343 



might occur between the Olenus schists and the Dictyonema 

 schists." The conditions in Scania appear to correspond 

 with those in Acadia, as the trilobites of the " Upper Olenus 

 Beds," (Div. 3a. and b. of the St. John Group), are mingled 

 with Dictyonema. But on the other hand, the upper or 

 typical Dictyonema beds (Div. 3c.) at St. John, have so far 

 yielded no trilobite 



Dictyonema also has associated with it at St. John, 

 several species of Brachiopods, — an Obolus somewhat like 

 0. Apollonis, Eichw, also an Obolella, a Linnarssonia like L. 

 misera, Bill; and a Lingula or Linguella. 



Dictyonema lived long enough in the St. John basin to 

 develop considerable differences in the appearance and 

 structure of the hydrosome. We recognize two varieties 

 which are probably the same with those mentioned by Dr. 

 Brogger as existing in Scandinavia, and we also observe 

 that the variety most common in Acadia differs from the 

 type in having more numerous, because more closely 

 set hydrotheca?. The variety Nbrvegicum characterised by 

 heavy cross-bars has changed from the type in the direction 

 of D. quadrangularis Hall, of the Levis shales, and the 

 special Acadian variety in the direction of Sir J. W. 

 Dawson's species D. delicatulum of the same shales. The 

 former variety is known to occur in the St. John basin at 

 the Arenig horizon (Div. 3d.), but the latter though known 

 at Quebec, has not been found here. 



Including the Dictyonema beds we now have in the 

 third or Bretonian division of the St. John group the fol- 

 lowing well characterized horizons : — 



a. Zone of Parabolina spinulosa (formerly described as 

 Zone of Leptoplastus stenotoides) . 



b. Zone of Peltura scarabeoides, contains also Dictyonema 

 flabelli forme. 



c. Zone of Dictyonema flabelliforme, typical development 

 of the species. 



?. Several hundred feet, fauna unknown. 



d. Zone of Dichograpt/is Logani and Tetragraptus, 4- 

 branchiatus, &c. 



