BRITISH DEVONIAN BRACHIOPODA. 23 



of which the dorsal septum passes. The angular projection near the centre of the dorsal 

 septum is in close apposition to that part of the loop where the two curved lamellae 

 unite, and, indeed, the dorsal septum and the loop seem to be united here. The 

 two curved lamellae which form the commencement of the loop are thin at their 

 origin, but they increase in thickness until they unite, and then from the point 

 of their union the loop is prolonged by a single rounded process in a straight or 

 slightly upward direction across the remaining portion of the distance between the 

 dorsal and ventral side of the spirals. At the end of this rounded process the loop 

 bifurcates in an upward direction, each branch of the bifurcation passing up inside 

 the hook-shaped attachment to the hinge-plate, and then as an accessory lamella 

 threading its way between the main coils to the end of the spiral. This long-extended 

 accessory lamella in each spiral is narrower than the coils which proceed directly from 

 the hinge-plate, as may be seen by scraping the spiral, when the coils of the accessory 

 lamellae soon disappear whilst the other coils still remain. The fourteen coils composing 

 each spiral are arranged in pairs, there being a greater distance between the second and 

 third and the fourth and fifth coils than between the first and second and the third and 

 fourth coils, and so on regularly throughout the 

 spiral. After the above description had been put 

 in type, Mr. Glass, receiving some more German 

 specimens of this species from Mr. Whidborne, 

 was able to make a perfectly clear and decisive 

 transverse section of the coils. A figure of the 

 section is here given, from which it will be seen ^ . , ^ . , , 



o Kayseria lens. Section enlarged. 



that, not only are the primary lamellae {a) much 



broader than the accessory lamellae {h), but that they are also slightly curved and 



thickened on their inner border. 



In tab. 51, fig. 25 r, of the Atlas of Prof. Quenstedt's work, ' Brachiopoden,' 

 the distinguished German palaeontologist figures what appear to be double spiral coils, 

 such as are more clearly to be seen in some of Mr. Glass's preparations. 



Thus it will be seen that this species, though bearing some resemblance to Atliyris in 

 its spiral arrangements, is in many respects unique. The prominent dorsal septum 

 and its connection with the loop, the shape and direction of the curved lamellae 

 composing the commencement of the loop, and the rounded process by which these 

 lamellae are continued, as well as the long extension of the accessory lamellae, distinguish 

 this species clearly from Atliyris, and, indeed, from all the other spiral-bearing genera 

 with which we are acquainted. The continuation of the accessory lamellae from their 

 commencement at the loop to the end of the spiral is especially notable. In Meristina 

 there is a simple loop ; in Whitjieldia this loop is continued by a bifurcation ; this 

 bifurcation is still further extended in Alhyris ; whilst in the species under consideration 

 the lamellae arising from the end of the loop are extended throughout the whole length of 



