﻿CRETACEOUS BRACHIOPODA. 



67 



opposite valve. The dorsal valve is also uniformly convex to about half its length 

 from the umbone, and then divides into three portions by the gradual rise of a wide, 

 slightly convex, mesial fold. Ventral valve moderately convex, with a deep, wide, median 

 sinus, beginning at about one third of the length of the valve from the beak ; the 

 remaining third being rather abruptly bent so as to meet the serrated margin of the 

 dorsal one. Front much thickened, flat, or forming a moderate or very deep concave 

 inward curve, with sharp lateral angles. Beak moderately produced, leaving a flattened 

 space between its ridges and the hinge-line ; foramen small, situated under the pointed, 

 slightly incurved beak, and margined by a narrow deltidium. Surface of each valve 

 marked by a variable number of small angular ribs (from sixty to seventy), longitudinally 

 indented near the margin and crossed by numerous concentric lines of growth which 

 become more numerous as they approach the margins. 



Proportions variable; a large specimen measured, length 10, width 12, depth 10 lines. 



Obs. This species somewhat approaches in shape and character the Bhynchonetta 

 Valangiensis, de Loriol, from the Etage Valangien (Neocomian) of Arzier in Switzerland. 

 Our species is larger, more transverse, (wider than long), and more obtuse at its beaks 

 than the Swiss shell ; this last has also a median depression in the mesial fold not 

 observable in any of the many specimens of the Upware species that have fallen under 

 my notice. In common with Bh. Valangiensis it sometimes presents that singular 

 frontal indented curve which we have endeavoured to represent in fig. 28. 



Position and Locality. Exceedingly abundant in the Lower Greensand of Upware ; 

 some large and fine examples may be seen in the Woodwardian Museum, Cambridge, 

 and in the collection of Mr. Walker at York. 



89. Rhynchonella Gibbsiana, Sow. Dav., Cret. Mon., PI. XII, figs. 11, 12. 



According to Mr. Meyer this shell occurs at Faringdon among the varieties of 

 Rh. nuciformis. Specimens have been found in the Lower Greensand of Folkestone, 

 Hythe, and Shanklin. A variety resembling Bh. lata, D'Orbigny (not Sow.), ' Pal. 

 Franc. Terrains Cretaces,' pi. ccccxci, fig. 14, occurs at Upware, as well as in the Perna- 

 bed at Atherfield, RedclifF, Shalford, and Sevenoaks. D'Orbigny has confounded two 

 species in his so-termed Bh. lata of Sowerby. 



90. Rhynchonella parvirostris, Sow. Dav., Cret. Mon., PI. XII, figs. 13, 14; Sup., 



PI. VIII, figs. 29, 29a. 



Lower Greensand, Shanklin, Isle of Wight. 



