Vol. 6^.~] ON FULLEES'-EAETH BRACHIOPODA. 427 



ACANTHOTHYEIS MIDFOEDENSIS, Sp. 110V. (PI. XXVIII, figS. 2a-2c.) 



T.l. Doultin2>Bridge Quarry, gear Doultina: (Somerset). 

 H. Pollers' Earth (Knorri-Clays). 



n- 



<Jolln. L. Richardson. 



Diagnosis. — Shell transversely oval, the width being greater 

 than the length, lenticular, moderately convex, margins sharp and 

 thin. It is coarsely ribbed (about eighteen on each valve), and 

 the spaces between the ribs are imbricated. The ribs themselves are 

 sparsely ornamented with spines, which are irregularly distributed — 

 the greatest number being on the ribs nearest the lateral margin of 

 the shell. The ventral valve has its greatest width and thickness 

 near the centre, from which a broad sulcus extends to the anterior 

 margin, forming a broad fold which is about a third of the width of 

 the shell in breadth. It usually contains four ribs, which are almost 

 devoid of spines. The beak is short and sharply recurved at its 

 extremity, so as almost to touch the umbo of the dorsal valve. The 

 apical angle is very wide, so that the hinge-line is nearly straight. 

 The dorsal valve is convex, gradually sloping from the centre towards 

 the anterior margin, and has no elevation corresponding to the 

 mesial sulcus of the ventral valve. 



R em arks. — Acanthothyris midfordensis differs from A. spinosa 

 (d'Orb.) of the ' Oolithe ferrugineuse,' near Bayeux, by its more 

 lenticular shape, by being less globose, larger, and having a wider 

 apical angle; but resembles A. spinosa in the irregular distribution 

 of its spines, which are few in number. It is easily separable by 

 these characters from flat forms of A. spinosa. 



Specimens from Midford differ somewhat from that figured, which 

 came from Doulting, in having a few more ribs, so that in this 

 respect the species is a little variable. 



The fossil is very characteristic of the lower portion of the Fullers' 

 Earth of the Bath-Doulting district, and has been found at the 

 Farmcombe and Doulting-Bridge Quarries ; between Doulting and 

 Cheyiinch ; in the railway- and road-cuttings, and at the Fullers'- 

 Earth Works, Midford ; also at the quarry situated about a mile 

 east of Paulton Church. 



Atjlacothteis Mandelslohi (Oppel). (PI. XXVIII, figs. 3 a-S c.) 



1857. Terebratula Handel slofti, Oppel, 'Die Juraforrnation ' p. 495. 



1858. Terebratula alveata, Quenstedt, ' Der Jura ' p. 494 & pi. Ixvi, fig. 22. 



1871. Terebratula alveata, Quenstedt, ' Die Brachiopoden ' p. 349 & pi. xlvii, 



figs. 47-50. 

 1884. Terebratula (Waldheimia) Mandelslolii, Oppel ; E. Deslongchamps in 



A. d'Orbigny's ' Paleontologie Prancaise : Terrain Jurassique — Brachiopodes ' 



p. 295 & pi. lxxxv, figs. 3-5. 



Diagnosis. — Shell rhomboidal, longer than wide, the greatest 

 width being near the centre of the shell, whence the surface slopes 

 towards the beak and towards the anterior margin, which is some- 

 what rounded. The edges of the valve are sharp ; shell-surface 

 smooth. The ventral valve slopes from the centre of the shell 

 towards the lateral margins, a steep roof-like elevation being 



