18 THE BIlACniOPODA. 



every way witli the type French specimens, showing two slight 

 farrows in the ventral valve oj)posite the two ridges on the dorsal, 

 and some of our specimens show the formation of a small extra 

 biplication, so well brought out in Mr. Deslongschamps' plate. 

 Taken as a whole Tereh. Fernji seems to vary somewhat in 

 dimensions, but the disposition of its folds is characteristic ; one 

 variation is longer and less deep, but these are the only differ- 

 ences between them and the iy]}Q specimens, into which they 

 gradually merge. 



Dimensions. — Typical specimen — Length 14, breadth 11, depth 

 11 lines. Another typical specimen — Ltngth 15, breadth l\h, 

 depth 10 lines. Long variety — Length 15, breadth 11, depth 9 

 lines. 



Localities. — (British) near Oborne (Dorset); (foreign) the whole 

 east of France. 



11. — Terebratula sphaeroidalis, Sowerly. 



1825. Terebeatula spnAEROiDALis, Soiv., Min. Conch., plate 

 ccccxxxv, figure 3. 



1857. ,, SPHAEROIDALIS, Dttv., British Brach. 



Palseont. Soc, plate xi., figures 9-15 only. 



1873. ,, SPHAEROIDALIS, E. Deslonqscliamps, Brach. 



Terr. Jurass., x^lates 79-82. 



This is one of the commonest species in the inferior oolite, and 

 shows a great deal of variation in form. Messrs. Davidson and 

 Deslongschamps have given a great many figures illustrating all 

 the j)rincipal variations. The French specimens figured by E. 

 Deslongschamps are of extremely large size, and I have not seen 

 any British specimens which at all equal them. Mr. Deslongs- 

 champs observes of this species that it varies in passing from one 

 bed to the other, that it does not occur in the zone of Opalinus 

 nor of Murchisonro, where it is replaced partly by Terel. conglo- 

 lata and partly by Terel. Eudesi. That it first appears in the 

 Am. Sauzei beds, where it is small and often deformed. That 

 in the zone of Am. Humphriesianus, it is common, and all the 



