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SUPPLEMENT TO THE 



drawings of the shell and its interior spirals with the name of Retzia d'widua. He also 

 shows that the extremities of the spiral coils were directed towards the lateral margins 

 of the shell, as had been previously described by Schnur, 



In the same year Emanuel Kayser, at p. 54 of his memoir ' Die Brachiopoden des 

 Mittel- und Ober- Devon, der Eifel," names this species Betzia lens, but gives no figure 

 of the spirals. Though Schnur and Quenstedt had figured the spirals of this species, 

 yet these distinguished palaeontologists were unable to trace the attachments or the loop 

 in their German specimens. 



Mr. Whidborne, having procured a number of specimens of Kayseria lens from 

 Hope's Nose, forwarded them to Mr. Glass, together with some German specimens of 

 the same species. I also procured for Mr. Glass a number of German specimens from 

 Dr. Kayser and others. By the aid of these, especially the German specimens, Mr. Glass 

 was enabled to determine in the most clear and satisfactory manner all the peculiar 

 internal arrangements of this species, as they will now be described. 



In the interior of the dorsal valve there is a 

 septum, which extends to about half the distance 

 between the beak and the anterior margin. This 

 septum is somewhat triangular in shape, the base 

 of the triangle being formed by the dorsal valve, 

 and the apex being extended towards the opposite 

 or ventral valve. This latter part of the sejitum, 

 as we shall presently see, is connected with the 

 loop. The septum after leaving the valve from 

 which it originates soon becomes comparatively 

 thin, but the apex of the septum is somewhat 

 thickened at the point where it unites with the 

 loop. The spirals are disposed in the shell in 

 the same manner as those of Athi/ris, and each 

 spiral consists of about fourteeen coils, that is, 

 of seven principal coils, arising from the hook- 

 shaped attachments to the hinge-plate, and seven 

 accessory coils, arising from the bifurcation 

 at the end of the loop. The primary lamellae 

 after leaving the hinge-plate proceed for a short 

 distance downwards, then they suddenly bend 

 backwards, forming a broad rounded curve facing the bottom of the dorsal valve. At 

 about one third of their length they give off' two short lamellae, which go straight 

 across between the spirals, and converging unite at a little more than half way between 

 the dorsal and ventral side of the spirals. These lamellae bend shghtly outwards before 

 coming to their point of union, thus forming when united a circular bay, through the centre 



Kayseria lens, enlarged. 



Fig. 1, showing spirals: a, attachments of primnry 

 lamelliB to hinge-plate; ^, loop; S and rf, accessory 

 coils ; c, principal coils. 



Fig. 2. Longitudinal section : letters indicate same 

 parts as in Fig. 1 ; s, septum. 



Fig. 3. Transverse section : d, dorsal valve; v, ven- 

 tral valve ; s, septum ; g, loop. 



