part 1] aAULT and lowee geeensand neae LEioHTOisr. 75 



Of the 28 species and varieties named in our previous paper (L.W., 

 p. 262) :— 



5 had been found previously in England only in the Lower Greensand ; 

 but two of these are recorded from Continental Tourtias, and other 

 two from the Mamraillatus Beds of Northern France. 



2 had been found as rare fossils in Lower Greensand and also in the 

 lower part of the Upper Cretaceous of England. Both are Tourtia 

 shells. One of them, Terebratula capillata, is the commonest fossil 

 of the limestone. 



8 (or, including Terehrirostra lyra var., 9) had been found only above the 



Lower Greensand, four occurring in the Gault or Red Chalk and the 

 remaining at higher horizons only. But one or two of the eight are 

 now recognized as occurring in the Upper Aptian of the South of 

 France.^ The Tourtias are known to contain six of the eight. 

 4 were new to England, but were previously known in one or other of 

 the Tourtias. 



9 were described as new species or varieties. 



28 



In their argument Dr. Kitchin & Mr. Pringle mention five of the species by 

 name (K.P., p. 4), but do not refer, except in general terms, to the other 23. 



Among the eighteen or twenty provisional determinations, in addition to 

 the above, resulting from Walker's later work {antea, p. 45), not more than 

 two or three are species known in this country ; but nearly all are Tourtia 

 forms. 



So far from this, the most abundant and most closely studied element of 

 the fauna, requiring the idea of an overturn, it appears to afford actual 

 disproof of the hypothesis. 



Correlation with the Tourtias is useless for any narrow and critical demar- 

 cation of age, since the Tourtias are known to occur at different horizons 

 where actually intercalated in the Cretaceous sequence ; and, where they form 

 the base of that sequence and rest directly on the much older rocks, they 

 are ' condensed ' deposits, probably covering a long period, and they then 

 generally contain many fossils not known to occur in beds which lie above 

 the Gault where it is actually present. 



The absence from Shenley of the common species of the Upper Greensand 

 and Lower Chalk has already been commented on (p. 45). 



The hypothesis of the intermingling of two limestones of different horizons, 

 one presumed to contain, besides its own fossils, others derivative from the 

 Lower Greensand, raises many real difficulties in the place of an imaginary 

 one ; and has no basis, so far as the brachiopods are concerned. 



Terebratula capillata deserves a further word, as its history is typical of 

 that of several of the commoner brachiopods of the limestone. The form 

 occurs as a rarity in the Lower Greensand of Upware and in the Red Chalk. 

 It is plentiful in several of the Tourtias, and is found also in the French 

 Mammillatus Beds. Its profusion at Shenley, where it is ' in full evolution,' 

 exhibiting a very wide range of varieties (L.W.,p. 249), led Walker to propose 

 that we should distinguish the limestone as ' the Zone of Terebratula capillata,' 

 which he regarded as the characteristic fossil of the bed (L.W., p. 250). 

 The shifting sand-banks of the Lower Cretaceous strait afforded no oppor- 

 tunity for the establishment or preservation of a ' reef-facies ' in the locality 



^ W. Kilian, ' Lethsea Geognostica: II, Das Mesozoicum ' vol. iii, 1913. 

 The species are Terebratula dutempleana d'Orbigny (p. 306), and (somewhat 

 doubtful) Rhynchonella grasiana d'Orbigny (pp. 309, 361). Another species 

 mentioned is Rhynchonella lineolata Phillips (pp. 307, 361), but this was 

 already known as a Lower Cretaceous form in England. 



