T]ie Use of Gryphcca in Correlation. 267 



or beak-like. The shell is broken, but at the length of 42 ram. has 

 a breadth of 32 mm. 



The holotype is beekitised and was collected in the Blue Lias near 

 St. Donats Castle. Beekitised Gryphscas, agreeing with Sowerby's 

 specimen in size and character, are exceedingly abundant in the 

 limestone reefs forming the shore jnst west of St. Donats Bay, 

 Glamorgan. 



It is likely that these are topotypes of Sowerby's species ; 

 ammonites are not commonly found in those beds, but the horizon 

 is the lower part of the hucMandi zone (the Vermiccras or rotator 

 .«ub-zone). Comparable forjus are found on the Dorset coast at 

 iipproximately the same horizon (W. D. Lang Coll. 4143-6). 



Gryj)haa incurva Sow. 

 Cf. G. arciiata Lamarck. 

 The chief characters of this species are the following : — 



1. The arched valve makes much more than one complete turn ; 

 it frequently rej^resents one and a half whorls. 



2. The area of attachment is very «m.all and is concealed in adult 

 shells by the curving of the valve. 



3. The shell increases very slowly in breadth, and the breadth 

 is little more than a half the total length (measured across the whorl). 

 In the holotype, the breadth of the arched valve at its widest point 

 is 41 mm. ; the diameter or greatest length is 73 mm. 



4. The beak does not ap>pear to be oblique at the apex in a com- 

 plete specimen. 



5. A prominent sulcus is present en the shell from an early stage 

 in development. 



It must be pointed out again that this name has been frequently 

 misapplied, and emphasis must be laid on the extreme curvature of 

 the left valve of this species. 



Tlie holotype (British Museum of Natural History, No. 43343) is 

 a specimen from Fretherne, Glos. The horizon is the huchlandi 

 zone (probably the Agassiceras sub-zone). Identical forms are 

 known from Purton Passage, Glos. (J. W. Tutcher Coll.) ; from 

 Bengeworth, near Evesham, Glos. (L. Richardson Coll., L.L. 16 

 and L.L. 11); and from the railway cutting near Bridgend, and 

 other parts of Glamorgan. 



It is, perhaps, desirable to explain why SoAverby's specific name is 

 used here in place of G. nrcuata Lam., which is supposed to be 

 synonymous. Notwithstanding the similarity between the two, 

 there is no proof of identity. Even if the two species can scarcely 

 be distinguished it does not necessarily follow that they are members 

 of the same lineage, and it is therefore preferable to use Sowerby's 

 name for the specimens from the English Lias. 



Note on the Cliff Section at Fretherne, Glos. 

 The low river cliffs at Hock Crib, Fretherne, about 8 miles south 

 of Gloucester, were examined primarily in order to determine the 



