36 



TYPE AMMONITES— VI 



Oct. 

 1926 



Table VIII — continued 



Age & Hemera 

 Paravirgatitan 

 8. lyditicus 



7. paravirgatus 



6. pectinatus 



5. pringlei 



4'. Wheatleyites 



Holcosphinctean 

 3. pallasioides 



2. inflatum 



I. bivius & grandis 



Long Crendon 



8. Pebble or Lydite, 



(5") 

 7. Thame Sands 

 (80') 



3. Hartwell Clay 

 2. Crendon Clay 



Isle of Purbeck 



Rotundum 



nodules 

 Crushed Amni. 



Shales 



White Septarian 

 Band 



Oil Shales 



Swindon 



8'. Upper Lydite i 

 8. Swindon Clay 

 7. Lower Lydite 



6. 5. 4'- 



Sands & Clays 



4. Marly Sandstone 



Sands with 

 Doggers 



Clays above 

 Brickyard of 

 Kings Hill . 



Clays in 

 Brickyard of 

 Kings Hill 

 (Hill's Brick- 

 yard) 



The thickness of the Thame Sands was measured, by use of a 

 level, up Barrel Hill, Long Crendon, with the assistance of Mr. 

 Waddington. Besides the named sands — Thame Sands, Crendon Sands, 

 a new term, and Littleworth Sands( = 25) — other Crendon beds 

 develop as sands locally in Bucks-Oxon ; so correlation by lithic 

 character cannot be trusted : to avoid criss-cross correlation, position 

 in regard to other beds and faunal contents must be carefully noted. 



The age-name Holcosphinctean is introduced in place of Pseudo- 

 virgatitan, as Pseudovirgatites may not belong to this age. 



There are several interesting points in the above correlation : — 

 Leucopetrites leucus (T.A. CCCVII, 1922) received its name because 

 its chambers were filled with a white (Afuxot) matrix, although 

 the specimen itself was embedded in a particularly green marl. In 

 Hounstout the matrix of Leucopetrites is a white cement stone. This 

 may be only a coincidence ; but it may mean that the white cement- 

 stone deposit once extended much further northwards. 



Prof. A. Pavlow (Class. Strata ; Q.J.G.S., lii, 1896, 542), shows, 

 in his correlation-table (facing p. 548), at certain localities in Russia, 

 giganteus beds, consisting of glauconitic sands and sandstone, overlying 

 beds with Virgatites. The lithic hkeness to the deposit of Long Crendon 

 and the position similar to that obtaining in the Isle of Purbeck, with 

 regard to the Cement Stone ammonoids and Virgatites, may be only 

 coincidences ; but they certainly prompt the query whether the " large 

 ammonites of the giganteus-iypt," which Professor Pavlow quotes for 

 these beds from Syrzan, Simbirsk and Moscow, may not be species 

 of the Buckinghamshire glauconitic beds — Behemoth, Glaucolithites and 

 Leucopetrites ; for the nomenclature at the time he wrote would allow 

 such forms only his given designation, since they are large and they 

 resemble giganteus, but had no precise names. 



