608 ON AMMONITES PEOM THE INFEEIOE OOLITE OF DOESET. 



Toococeras Orbignyi (Baugier and Sauze), d'Orb. Terr. Jurass. 

 pi. 232. figs. 1, 2. 



From near Sherborne. 



Since the above paper was written, we have made out the Yeovil 

 sands more clearly from some fresh sections. Just below the Mur- 

 chisoncB zone (the equivalent of the Gloucestershire Pea-grit) come 

 about 30 feet of sands. Then comes a marly bed about a foot thick, 

 containing Harpoceras opalinum, Lytoceras torulusum, Waldheimia 

 anglica, and Rhynclionella cynocephala. Below this come about 

 100 feet, sometimes more, of sands in which Lytoceras jurense (Zieten) 

 occurs along with Harpoceras Moorei (Lyc.) &c. These lower sands 

 therefore belong to the zone of L. jurense. 



On the vexed question as to whether these latter belong to the 

 Lias or Oolite 1 have not formed an opinion. 



Discussion. 



The Peesident bore testimony to the great industry and skill 

 shown by the young author in collecting from the richly fossiliferous 

 beds of the Inferior Oolite of Dorsetshire. He pointed out the 

 importance of having sections of perfect specimens of Ammonites 

 made, so as to show the relation of the body-chamber to the others 

 in these shells. 



Mr. Htjdleston referred to the difference between the views of 

 Mr. S. Buckman and his father, Prof. Buckman, as to the value of 

 the zones of the Inferior Oolite and the geological age of the Yeovil 

 Sands. 



Mr. Chaeleswoeth remarked on the absence of phragmocones of 

 Belemnites in Chalk rocks, and of the opercula of Ammonites from 

 many Jurassic rocks. 



Prof. Seeley denied the universal absence of phragmocones of 

 Belemnites in the Chalk, and stated that it might be accounted for 

 by the condition of preservation of the fossils. In the same way the 

 absence of aptychi might be accounted for by the general explana- 

 tion of such facts given by Mr. Sorby, who showed that fossils 

 composed of the unstable substance aragonite were rarely preserved. 



Prof. Blake thought that many of the so-called species of Ammo- 

 nites would prove to be only varieties of well-known ones. He 

 confirmed the views of the President as to the value of determining 

 the proportion of the body- whorl. 



The Peesident stated that Mr. Buckman had adopted the views 

 of classification which he had himself long ago insisted on. He 

 accounted for the frequent absence of aptychi by the fact that the 

 body-chamber is not usually broken open. He also agreed with Mr. 

 Charlesworth as to the general but not universal absence of the 

 phragmocone in Belemnitella, and with Mr. Blake that many of 

 these Ammonite-forms could not be regarded as distinct species. 



