53 
In the Concarunn zone of Gorton Downs, occurs a small 
dwarf form. This is probably a forerunner of the above species, 
though it is not so coarsely ribbed. It possesses very few 
spines. Possibly it may be best distinguished by the varietal 
name cortonensis. 
Acanthothyris tenuispina (Waagen) P 
1867.— Rhynchonella (. Ilemithyris ) tenuispina, Waagen, Zone 
Amm : Soicerbyi. Greogn : Pal. 
Beitrage, Bd. i., Heft, hi., PI. 
xxxii., Fig. 6. 
Certain specimens which occur in the Humphresianum- zone 
at Oborne, and at Louse Hill, are probably referable to this 
species, because they possess the numerous ribs and spines, and 
also the marked, raised mesial fold. They differ only from 
Waagen’s figure in being larger, and somewhat broader; but 
the latter character is not invariable. From Acanthothyris spinosa 
they are separated by finer ribbing and more pronounced fold; 
in fact, in general appearance they are like Acanthothyris 
panacanthina , but from this the fold separates them, while the 
valves are more convex. 
Acanthothyris panacanthina, Buckman and Walker. 
1851— Rhynchonella senticosa , Davidson, Oolite Brachiopoda, 
Pal. Society—Plate xv., figure 21, page 73. 
1878— Rhynchonella senticosa, Davidson, Proc. Dorset Club. 
Brachiopoda of Inferior Oolite—Plate iv., figure 20. 
1883— Rhynchonella senticosa, S. S. Buckman. Brachiopoda, 
Proc. Dorset Club. 
Also Rhynchonella senticosa, from the Inferior Oolite, of 
various English authors. 
NO !&-Terebratulites senticosus, von Schlotheim. 
Terebralula senticosa, von Buch. 
Hemithiris senticosa, d’Orbigny. 
Acanthothiris senticosa, d’Orbigny. 
Terebratula senticosa, Quenstedt, 
and not the Rhynchonella senticosa from the Middle Oolites of 
foreign geologists. 
