1926 SYSTEMATIC 37 



Dec. 



In addition to Lencopetrites in the Cement Stone of Hounstout, 

 there is some reason to think that Behemoth lapideus may be found in 

 the cliff, judging by large, much-battered relics lying on the shore among 

 faUen blocks. 



A few j'ears ago, during a visit to Ringstead Bay, Dorset, 

 I discovered the position of Rhynchonella portlandica in the faulted mass 

 of Portlandian by Holworth House. The following section was noted, 

 but the thicknesses are only guess-work, as I did not climb much above ' 

 the Rhynchonella seam. 



G. Holworth 



5. Portland Limestone, Flinty Series 



4. Limestone below Flinty Series, about 30' 



3. Limestone, more or less sandy, about 10' 



2. Brown earthy sands, about 8' 



I. Marly to clayey seam with Rhynchonella portlandica, Orbiculoidea 

 " humphriesiana," Orbiculoidea smooth (cf. 0. glabella, S.B., T. A. 

 DXXXIVb) and Lingula " ovalis." This seam is about two inches thick, 

 and these fossils were not found above or below. 



This section may be checked by the lower part of that given by 

 H. B. Woodward, op. cit. p. 194. It may be assumed that the Rhyn- 

 chonella horizon is about that of the Massive Bed of Hounstout. 



The horizon of Rhynchonella portlandica is thus noted particularly 

 because it is so remarkably like Rhynchonella loxia, Fischer, of the 

 Volgian of Russia. Both are cynocephalous species associated with 

 ammonoids having virgatite ribbing ; but R. loxia is capillate (striate) — • 

 S. Buckman Brach. Burma ; Pal. Ind. iii (2), 1917 (1918), p. 57, 

 PI. xviii, 30, 31 ; while no such character has been detected in R. 

 portlandica. On the other hand, R. subvariabilis is capillate, and might 

 be considered near to R. loxia both in this character and in position ; 

 but the specimens which have been found by Mr. Waddington and 

 myself so remarkably like R. subvariabilis, and apparently much in the 

 same position as the spwcies from Potteme, do not seem to show any 

 capillation. 



The position of Orbiculoidea is thus noted because it has now been 

 found in beds which seem to work out as practically on the same horizon 

 in Dorset and Bucks. This, too, may be only a coincidence. The very 

 distinctive little Orbiculoidea humphriesiana ; Blake sp., is quite possibly 

 not the same as Orbicula humphriesiana, J. de C. Sowerby, except in 

 being ribbed. It and a smooth form are minute, no bigger than a large 

 pin's head : they are unattached and very difficult to find : the 

 Orbiculoidea glabella at Crendon is larger and attached. 



If the rotundtim beds of Chapmans Pool are correlated with the 

 Littleworth Lydite Clay, a point wherein the Geological Survey, Dr. 

 Neaverson and myself are agreed, and if the Littleworth Lydite Clay 

 be correlated with the Long Crendon Lydite (or Pebble) Bed, which, 

 in face of the ammonoid and stratigraphical evidence, it will be difficult 

 to dispute, then there is a big non-sequence at Long Crendon above 

 the Lydite Bed — all the Virgatitan beds of Hounstout, or all the beds 

 from about the top of the Massive Bed to the top of the rotundum beds — 

 according to Blake, about 160 feet — are missing. There is a bigger gap 

 at Swindon, since the Glauconitic Beds of Crendon are absent from 



