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SUPPLEMENT TO THE BRITISH 



T. rigida, Sow., are distinct species, and since Mr. Meyer takes a similar view it will be 

 preferable to maintain them separate. 



T. gracilis is wider and more circular in shape than T. rigida. The dorsal valve is 

 also much flatter and the ribs comparatively stronger. It is also a much larger shell, 

 some specimens from the Upper Chalk of Vaels having measured nearly half an inch 

 in length and breadth, while some Swedish examples have attained to nearly similar 

 proportions. 



29. Terebratulina rigida, Sow. Dav., Cret. Mon., PI. II, figs. 16, 17. 



Terebratula rigida, Sow. Min. Con., vi, p. 69, tab. 536, fig. 2, 1829. 



Erom the many synonyms collected by Dr, Schloenbach it appears that this 

 species has been often referred to T. gracilis. It is, however, always smaller, more 

 convex, and comparatively longer than T. gracilis. It occurs in the Kentish Chalk, the 

 Upper Greensand of Cambridge, Grey Arenaceous Chalk and Red Chalk of Speeton, the 

 Blue Gault of Norfolk, &c. 



30. Terebratula ovata, Sow. Dav., Cret. Mon., PI. IV, figs. 6—13 ; and Sup., PI. II, 



fig. 14, and PI. VII, figs. 1, 1 a, b, c (?). 



The loop is short and simple. Specimens have been found in the Upper Greensand 

 of Warminster, Dunsconibe, Pinney Cliff, and the Isle of Wight, &c. When young the 

 shell is ovate, with its valves regularly convex ; the depression near the front is observ- 

 able in adult individuals only. A young specimen in the Cambridge Woodwardian 

 Museum (PI. VII, fig. 1) is stated to have been obtained from the Greensand of 

 Blackdown, which beds are considered by Renevier, Etheridge, and others, to be an 

 equivalent of the Lower Greensand or Gault, especially of the upper part of the last-named 

 formation. Brachiopoda are extremely rare at Blackdown ; I have never seen or heard 

 of more than this specimen and two or three of a Bhjnclionella. 



31. Terebratula arcuata, A. Boemer. Dav., Cret. Mon., PI. IV, fig. 14 ; Sup., 



PI. II, fig. 16. 



Terebratula rugulosa Morris. Dav., Cret. Mon., p. 49, pi. iv, fig. 14, 1847. 



— arcuata, A. Roemer. Kreid., p. 44, pi. vii, fig. 18, 1841. 



— — Schloenbach. Ueber die Bracb. der Nord. Cenoman-Bildun- 



gen, p. 451, pi. xxi, fig. 12, 1841. 



