TilE BilACHtOPODA. 15 



7. — Terebratul.v ixfra-oolithica, IE. Besl. 



1871. Terebratula ixfra-oolitiiica, E. Beslongschamps, Brach. 

 Terr. Jiirass., plate Iviii., and plate lix., 

 fig. 1, and plate Ix., fig. 2. 



1878. Terebratula ixfra-oolithica, Davidson, Brach. Palrcont. 

 Soc. supplement, plate xviii., figs. 8-9. 



The type of this species is given by Dcslongschamps in pi. 58, 

 fig. 7. This species is very variable, as he shows -well, -vvith the 

 chief variations being in the disposition of the biplieations. Some 

 also have hardly any or no trace of biplication, as sho-wn in his 

 figures 1, 2, 5, &c. From this district I have obtained specimens 

 agreeing exactly with his types, and have also obtained the 

 various varieties except the peculiarly large one figured on plate 

 60. We have also some rather thick varieties of this shell with 

 the biplieations well marked. Mr. Deslongschamps says of this 

 species, that it is a sort of intermediate between Tereh. inter- 

 media and Tereh. (jlobata. Both of those, however, come 

 very much later in geological age than this species. I consider 

 that Ter. infra-oolithica, in spite of its variability, is easy to 

 distinguish, at least from any species from this district. It 

 would not be taken for the young of Ter. pcrovalis because of its 

 small circular foramen and generally more circular form. Some 

 varieties approach Ter. Eudesi, but the beak does not curve over 

 so much, and the valves are far less convex. The varieties with- 

 out biplieations very much approach the young of Ter. ampla 

 Buck., but are not cj^uite so broad. Tereh. infra-oolithica and Tereh. 

 dorsoplana, Waagen, are also much alike, but the carinated larger 

 valve, and peculiar beak ridges, &c., of the latter distinguish 

 it easily. 



Terel. infra-oolithica has been found in the Jurense zone in 

 Gloucestershire. These specimens are figured by Mr. Davidson, 

 supplement plate xviii., figs. 8 and 9. They are slightly longer 

 than specimens from this district, which agree better with E. 

 Deslongschanip's figures. 



