444 ]\Ir. >S. S. Buck man on 



terminal surface is rough and irregular and appears to liave 

 been cartilaginous. 



The structure here described I believe to be the typical 

 Ichthyosaurian mode of articulation of the neural arch \n 

 vertebrae behind the neck, about as characteristic as is the 

 presence of zygosphene and zygantrum in the neural arch of 

 an Ophidian. It is not quite unique, being also met with in 

 the neural arches of the caudal vertebree of certain Plesio- 

 saurs from the Kimeridge Clay, much as the Ophidian type 

 of neural arch is met with in certain Lacertilia. 



The physiological interest of the single zygapophysial 

 facet is the evidence it affords as to the absence of lateral 

 motion of the body, as indicated by absence of resistance 

 to movement of the arches upon each other. The greater 

 length of the postzygapophysis may show a small vertical 

 gliding movement of the prezygapophysis against it, which 

 would be consistent with a vertical movement of the tail, 

 a diving habit, and a folding of the tail beneath the body in 

 swimming. 



LXX. — Brachiopod JS'omendature : The Terebratulaj of the 

 Crag. By S. 8. BuCKMAN, F.G.S. 



The English Tertiary deposits known as the Coralline Crag 

 and the Ked Crag are famous for yielding Terebratulce, some 

 of which attain very large dimensions. For many years, on 

 the authority of Davidson^ these Crag Terehratulce have been 

 regarded as one species, and have been identified with the 

 Hanoverian Terehrut'ula grandis^ Blumenbach. 



During some recent curatorial woik^ having occasion to 

 examine these Crag Terehratulce for the purpose of their 

 exhibition, I came to the conclusion that the identification of 

 any of them with T. grandis could not be sustained. Further, 

 the material examined showed that there were at least four 

 fairly distinct forms, which could be distinguished as 

 follows : — 



1. A large oval form. 



2. A large elliptical form. 



3. A medium-sized, narrow, elliptical form. 



4. Small, aged forms, which are dwarfs. 



Thus there are three forms which diflfer considerably in 

 shape and one series of dwarfs, many of which are not the 



