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SUPPLEMENT TO THE BRITISH 



82. Rhynchonella dimidiata, Var. convexa, Sow. Dav., Cret. Mon., PI. XI, figs. 



6—14; and PI. XII, fig. 24. 



Rhynchonella latissima, Dav. Cret. Mon., p. 82, pi. xi, figs. 6 — 14 ; and pi. xii, 



fig. 24 (not R. lata, or latissima, Sow. ?). 

 Terebkatula convexa, Sow. Fitton, Trans. Geol. Soc, 2nd ser., vol. iv, pi. xiv, 



fig. 12. 



This variety is far less transverse than the preceding one, being at the same time 

 more convex. The mesial fold is scarcely raised, and the shell is marked by as many as 

 sixty small radiating ribs when full grown. Some specimens, such as the one I 

 represented by PI. XI, fig. 13, present the small ribs of the variety convexa up to two thirds 

 of the length of their valves, when, after a pause or interruption, the ribs become 

 suddenly fewer and considerably stronger and larger, Specimens with this variation in 

 shape and character are very abundant in the same localities where the typical form 

 occurs. I cannot agree with Dr. Schloenbach when he proposes to consider the small 

 shell, PI. XII, figs. 28, 29, 30, from Chardstock as another variety of Rh. dimidiata. 



The variety convexa is very abundant in the Upper Greensand of Warminster. A 

 smaller and more gibbous form of the same is plentiful in the Hibernian Greensand 

 (Upper Greensand) or ' Zone of Inoceramus Crispi ' at Woodburn, near Carrickfergus, 

 County Antrim, and at Moneymore, County Derry, Ireland, where it has been collected 

 by Messrs. Tate, Judd, and others. 



83. Rhynchonella (lata) latissima, Sow. Dav., Cret. Mon., PI. XI, figs. 15 — 22 (not 



6—14, nor PI. XII, figs. 24, 28, 29, 30). 



Mr. Meyer is of opinion that the typical and true Rh. latissima, Sow., from the Faring- 

 don Sponge-gravel is distinct from the so-termed Rh. latissima {dimidiata) of Warminster 

 and Le Mans ; also that it is distinct from d'Archiac's figures, which most probably 

 represent Rh. dimidiata. He adds that it would not only be safe but proper to 

 separate entirely Sowerby's Faringdon species Rh. latissima, Rh. depressa, and Rh. 

 nuciformis from any other forms that occur in the Chloritic beds or so-called Upper 

 Greensand of Chard, Chardstock, Warminster, the Isle of Wight, &c. ; and he even 

 doubts whether there are any English species of Brachiopoda common to beds below and 

 above the Gault. If my distinguished friend be correct in this respect, I cannot help 

 observing that many specimens I have picked up at Warminster, if not specifically 



