456 me. a. wade on the llandovert and [Aug. 191 1, 



(6) Graptolites. 



The graptolites are mostly forms which have been described fully 

 by Miss Elles and Miss Wood (Mrs. Shakespear), either in the 

 works already mentioned [9] & [10], or in their monograph on the 

 British Graptolites still in progress. 



Pigs. 10 a and 10 b, however, seem to be slight variations upon 

 Diplograptus (Ampleocograptus) perecccavatus Lapw. The enlarged 

 figures show the extraordinary spiny and irregular nature of the 

 thecse. This is commonly seen in the species from Trelydan and 

 Sale Dingles. 



Pig. 11 represents an interesting young specimen of Monograptus 

 vulgaris from the Tyn-y-llwyn outlier. The chief point of interest 

 is in connexion with the sicula. The early stages of the grapto- 

 lite suggest in a surprising manner Corynoides calicularis of 

 Nicholson. 1 



Fig. 10. — Amplexograptus per- 

 excavatus Lapw., magnified 5 

 diameters. 



Pig. 11. — Young form of 

 Monograptus vulgaris, 

 magnified 5, diameters. 



[Both specimens are from Trelydan 

 main dingle, about 100 yards down.] 



[The specimen is from 

 Tyn-y-llwyn.] 



In concluding the notes on the palaeontology of the area, I should 

 like to mention a feature which this study has indicated. When- 

 ever shales and deep-water deposits occur in the sequence, there 

 is a remarkable influx of types which are common to the similar 



1 • Monogr. Brit. Graptolitidae ' London, 1872, p. 132, fig. 74. 



