PAA a2 
Fics. 1 a—-d, 2 a-d, 3 a-d. Torquirhynchia cf. T. astieriformis (Wisniewska). Kimmeridg- 
ian, mutabilis zone. Sermérieu (Isere), France. B.M. BB. 45174-6. 
Fic. 5. Torquirhynchia inconstans (Sowerby) from the Kimmeridge Clay of Ringstead 
Bay, Dorset. Shows the nature of the articulation, the shape of the median ridge and the out- 
line of the muscle scars in the brachial valve. x14. B. 60368. 
Fic. 4. Transverse through the hinge plate of Septaliphoria paucicosta sp. nov. showing 
the form of the septalial plate and the crural base. This is part of section 4, 3 figured in text-fig. 
33. wz: 
Fic. 6. Transverse section of Septaliphoria paucicosta sp. nov. showing the median 
septum and septalial plates. This is part of section 3, 4 in the series shown in text-fig. 33. 5. 
Fic. 7. Transverse section of Acanthorhynchia (Acanthorhynchia) panacanthina 
(Buckman & Walker) showing the thickened nature of the hinge plates. This is part of section 
I, 9 in the series shown in text-fig. 24. 
Fic. 8. Transverse section of Zeilleria austriaca (Zugmeyer) showing the form of the 
septalium. Specimen obtained from the Rhaetian of Piesting Tal, Lower Austria. The “ peel ” 
from which the photomicrograph was taken was kindly made available to the author by Dr. 
D. A. B. Pearson. X5. 
Fic. 9. Transverse through the hinge plates of Lacunosella vaga sp. nov. showing the form 
of the falcifer crura. This is part of section 3, 6 in the series shown in text-fig. 14. 
