1926 SYSTEMATIC 33 



defective, but its likeness to Virgatites scythicus is so great that it is 

 figured in PI. DCLXXV. Its matrix is a blue sandy stinkstone — that 

 is, smelling when struck — which, however, may be a character of more 

 than one of the Portland-Sand beds. It is judged to have come from 

 the base of the Massive Bed (h). 



From a large fallen block of the Massive Bed, on the beach which 

 forms the western side of Chapmans Pool, and presumably from what 

 is its base, I obtained a considerable series of Rhynchonella portlandica, 

 Blake, (all crushed), mixed with a curiously rugose Exogyra (Figs 2, 3, 

 p. 32). Subsequently Mr. Waddington found this Rhynchonella in the 

 Massive Bed in situ, but not abundant. 



7. /. A few feet lower is another indurated sandy block, about 

 two feet thick, but no fossils were obtained. (This and the Massive 

 Bed appear to correspond to Blake's 14, 15, except in the matter of 

 thickness. Blake's 16 is below : it can be divided more than he has 

 done.) 



6. (16 [a]), e. Blue Sandy Marls, with more or less of stinkstone 

 bands : these are 40 or 50 feet in thickness, and extend down to about 

 the old road. According to the colouring of the Geological Survey Map, 

 No. XVI, 1855, this is the base of the Portland Sands. H. B. Woodward 

 (Ool. Rocks, V ; Mem. Geol. Surv'., 1895, p. 191) makes Lower Portland 

 Beds ( = Portland Sands) end with the Massive Bed. Blake carries 

 the beds 80-100 feet lower. 



Kimmeridge Clay : — 



5. (i6[b] ). d. Dark clays, no fossils found, perhaps 30 feet. 



4. (i6[c] ). c. Rhynchonella marls : they yield a Rhynchonella, 

 small Lamellibranchs, Cidaris spines and Belemnites : they are perhaps 

 15-20 feet in thickness. Mr. Waddington discovered the bed with this 

 fauna, and I confirmed it. The Rhynchonella is like R. subvariahilis, 

 Davidson, but is doubtful, because the specimens lack the longitudinal 

 striation mentioned by him : his original specimens came from the 

 Kimmeridge Clay of Potteme, Wilts. 



3. (i6[d] ). h. Lingula shales. Light-coloured arenaceous shales 

 with many Ltngulee. Blake mentions the LingulcB as about 40 feet 

 above Kimmeridge Clay, and that the line of separation from that clay 

 is " more or less arbitrary " (p. 195). The cliffs on the north rim of 

 Chapmans Pool seemed to show above the rotimdum beds a line of 

 demarcation, as if tfiere were a non-sequence ; but this would be far 

 lower than what Blake calls the top of Kimmeridge Clay. 



The Beds i6[b-l] were examined on the valley-side south of the 

 stream, between th«^ stream and the Coastguard Station. The Lingula 

 is not L. ovalis, Sowerby, which is doubtfully a Kimmeridgian species ; 

 but the Chapmans-Fool Lingula is little, if any, different from other 

 so-called Lingula ovalis found in quite other horizons of Portland Sand 

 and Kimmeridge Cl^y. As a dating fossil it is, probably, useless, but 

 must serve for the present. 



2. a'. Rotundum Clays, with nodules. A line of ammonoidiferous 

 nodules which is, under Hounstout, about 15 feet above the beach, 

 dipping to about 10 feet or less southwards, near the boat-house, yields 

 Lydistratites and Pallasiceras uncrushed, but the large specimens often 

 imperfect. 



I. a. Crushed Ammonoid Shales : The base of the cliffs and the 

 pavement of the beach show a multitude of crushed ammonoids, some 

 of quite large size. It is possible that they are neither Lydistratites nor 

 Pallasiceras, but Paramrgatites. The differences between these genera, 



