266 



Dr. A. E. Triteman- 



extremely common in the Lavernock Shales in the Cardiff district ^ 

 and in the lower angulata zone near Keynsham, Somerset.^ 



Gryphcea cf. dumortieri Joly. (Fig. 16.) 

 G. dumortieri Jolv. Les Fossiles du Jurassique de la Belgique, 



1908, pi. i, figs. 4-7. 

 G. sp. Dumortier. Dep. iiir. Bass. Rhone, pt. ii, p. 83, pi. xv, 

 . ^' 2. " 



This species is distinguished from 0. irregidaris by its smaller 

 area of attachment, which is not usually more than one-sixth the 

 length of the shell. The curve of the left valve amounts to about 

 one-half of a whorl. This species was described by Joly from the 

 Hettangian of Belgium ; specimens which appear to be identical 

 are found not uncommonly in the angulata sub-zone of Glamorgan 

 and around Radstock, Somerset. 



Fig. 7. — Prodissoconch of Ostrcea liassica Strick. x 8 approx. From the 

 Ostrcea Beds, Owtliorpe, Notts. 



Gryphcea dbliqiiata Sow. 

 Cf. G. arcuala var. rugosa Munst. Goldfuss, Petref. Germ., 

 y)l. Ixxxiv, fig. 2c only. 

 This specific name has been applied to many gryphajate forms 

 from various horizons in the Lias. It is necessary therefore to 

 emphasize the characters by which it is distingnished. 

 Sowerby pointed out that in his specie? — 



1. The attached valve does not form a complete whorl. 



2. The beak is twisted to the posterior side (Fig. 2h). 



3. The area of attachment is small. 



4. The shell is broader in proportion than in G. incurva. 



It may be added that the holotype of Sowerby's species (in the 

 British Museum of Natural History) shows a faint sulcus appearing 

 on the later part of the shell. The shell is not free from matrix, 

 but the apex of the shell appears to be broad and not detached 



1 A. E. Trueman, " The Liassic Rocks of the Cardiff District " : Proc. Geol. 

 Adsoc, vol. xxxi, 1920, p. 102. 



2 A. Vaugban & J. W. Tutcher, " The Lias of the Neighbourhood of 

 Keynsham "' : Proc. Prist. Nat. Soc, N.S., vol. x, 1903. 



