2 TRILOBITES OF GIRVAN. 



Lapworth, to whose labours Ave owe most of our knowledge of the stratigraphy 

 It may be summarised in tabular form as follows : 



Wenlock 



Tarannou 



Llandovery 



Caradoc Formation 

 Upper Llandeilo 



Blair, Knockgardner and Straiton Beds. Wenlock. 



, Drumyork Group. 



Part of Lapwortli's | t> ~ 



^ „. ■ . Bargany Group. 



{ Dailly Series { penim ^^ 



/ 



Newland's Series 



Ardmillan Series 



Barr Series 



Camregan Group . 

 J Saugh Hill Group . 

 I Mulloch Hill Group 



(Drummuck Group . 

 Barren Flagstone Group. 

 Whitehouse Group . 

 Ardwell Group. 

 Balelatchie Group 

 Stinchar Limestone Gi 



[ Upper Llandovery. 



Middle Llandovery. 

 Lower Llandovery. 

 Upper Bala. 



Middle Bala. 



p . . | 

 ne Group J 



Llandeilo. 



The terms employed by Mrs. Gray and some others in designating the various 

 horizons are shown in the last column of the preceding table, and express their views 

 of the correlation of the beds with their English or Welsh equivalents. The 

 correlation adopted by the Geological Survey (1899), and here given in the first 

 column, differs slightly from this, the Penkill Group being regarded as the equivalent 

 of part of the Tarannon, while the Camregan Group alone is considered to corre- 

 spond with the Upper Llandovery. The term Caradoc is used by the Survey 

 instead of Bala, and is made to embrace the whole of the Ardmillan Series, 

 including, at the base, the Balelatchie Group, which Mrs. Gray places as part of 

 the Llandeilo. The Stinchar Limestone Group is termed Upper Llandeilo by the 

 Survey. 



The classification of the Trilobita here followed is that adopted by Prof. 

 Chas. E. Beecher, of Yale University, in the translation of Prof. Karl von Zittel's 

 ' Text-book of Palaeontology ' (published 1900). This seems to be the most natural 

 and satisfactory arrangement so far proposed, and may be stated thus : 



Order 1. — Hypoparia. 



Family 1. Agnostidse. 



2. Harpedidae. 



3. Trimicleidse. 

 Order IT. — Opisthoparia. 



Family 1. Conocoryphidse. 



2. Olenidae. 



3. Asaphidie. 



4. Proetidae. 



5. Bronteidse. 

 0. Liehadida?. 

 7. Acidaspidae, 



