254 Messrs. Davidson & Morris on some species of Brachiopoda. 



the radiating strise are wanting, in the British Museum, as having 

 been received from the gray chalk marl of Dover. 



M. le Vicomte d'Archiac, in the very interesting memoir * 

 " Sur les Fossiles du Tourtia," has pointed out a very natural 

 group of the Terebratula, to which the two last-described species 

 evidently belong. They are well-characterized by having the 

 surface ornamented with numerous small rugae, which are more 

 or less prominent, very short, puckered, squamous, arcuate or 

 diverging either from the centre or the beaks towards the margin, 

 where they are always visible. The Ter. Verneuilli, d'Archiac, is 

 the typical form, and the allied species are the T. Murchisoni, 

 Keyserlingi, Tchihatcheffi, Gravesi and Leveillei, d'Archiac ; the 

 T. arcuata, Roemer, and our T. spinulosa and T. rugulosa. 



Terebratula sulcifera, Morris. PI. XVIII. fig. 7, 7 a, b. 



Shell obovate, somewhat pentagonal, ventricose ; valves nearly 

 equally convex, dorsal valve convex towards the beak, which is 

 produced and incurved ; foramen large, oblique ; deltidium wide, 

 transversely furrowed and margined by a slightly elevated ridge, 

 but generally almost concealed beneath the anterior part of the 

 foramen which nearly touches the ventral valve. The greatest 

 thickness of the dorsal valve is about the middle, from which ex- 

 tends a broad, flat, and not very deep sinus with a straight frontal 

 margin ; lateral margins sinuous ; the lateral margins near the 

 cardinal line of the ventral valve overlap those of the dorsal. 

 Both valves marked with concentric, somewhat imbricated ridges 

 with broader interspaces, and numerous radiating, nearly obsolete 

 strise, only visible in some specimens near the sides. 



Of this species there are many varieties in form, the extreme 

 one being that given in our fig. 7 ; others are much less gibbose 

 and even depressed, sometimes having a triangular shape, at 

 others being very much elongated or compressed laterally ; but 

 the concentric ridges, although distinct in all of them, are more 

 or less elevated according to age, the intervening furrows being 

 marked (when viewed under a strong lens) by slightly raised 

 granules. 



From the lower chalk near Cambridge, in the collection of 

 Mr. Bunbury, whose specimen is figured, and from Hockwold, 

 Norfolk, by Mr. W. Flower of Croydon. 



Terebratula squamosa, Mantell. PI. XVIII. fig. 8, a, b. 



Shell orbicular, or sometimes longitudinally ovate, valves nearly 

 equally convex ; foramen circular, entire ; deltidium rather large, 

 dilated at the base; surface marked with concentric squamose 



* Memoires de la Societe Geologique de Fiance, 2nd ser. vol. ii. p. 295. 



