6 TJwmas Davidson — Spiral-Beai-ing Brachiopoda. 



closely following the outer side of the first coil, ends near the place 

 where the principal stem gives off its connecting process q. Indeed, 

 Mr. Glass found in many specimens that this half coil lay much 

 closer to the first than to the second coil of each spiral. 



Now, as Mr. Glass has worked out very many specimens of 

 Ailiyris planosulcata, and as they invariably show the same results 

 and in the clearest possible manner, there can be no doubt as to 

 our jDOSsession of every detail in connection with the spiral arrange- 

 ments in the genus Atliyris, especially as these preparations of Mr. 

 Glass are fully corroborated by the specimens of Atlujns ambigua 

 which he also developed in a similar manner. 



Genus Meristella, Hall, 1859. 



The working out of the spiral processes and their attachments in 

 Meristella tumida does the Kev. Norman Glass the greatest possible 

 credit. Not only has Mr. Glass been able to develop the spirals, but 

 to take them entirely out of the shell, so that they can be examined 

 in every direction. He has also completely excavated the inner side 

 of one of the spiral cones, so that when held up between the ej'e and 

 the light the various convolutions can be seen as a transparency. He 

 likewise has been able to work out the attachment of the principal 



Fig. 4. Fig. 5. 



iferistella tumida, after Mr. Glass's preparations. 



coils to the hinge-plate and their complicated system of connecting 

 lamellae. All these admirably prepared specimens will be fully 

 illustrated in my forthcoming Supplement. As will be observed 

 from the two diagrams here given, and drawn from Mr. Glass's 

 specimens of Meristella tumida, the principal characters of the 

 Athjridce are maintained. The attachment to the hinge-plate at a, 

 the short prolongation of the lamella a, h, its bending backwards 



