NOTES ON THE BKITISH JUEASSIC BEACHIOPODA. 29 



LINGULA, Bruguiere, 1792. 

 Etjm. — Lingula, a little tongue. 



In this genus the valves of the shell are held in apposition 

 by nmscular action alone, and not by means of an hinge, as 

 in the case of Terehratula, Bhynchonella, etc. 



There is no foramen for the emission of the peduncle, 

 although there is a groove for its passage in the ventral 

 valve. Neither is there any shelly support for the labial 

 appendages. 



Unlike the majority of the Brachiopoda, the shells of 

 Lingulce are almost entirely composed of a horny animal 

 substance. 



This genus is represented in the strata under consideration 

 by eight species, four of which are characteristic of the 

 Lias and four of the Oolites. 



L. heayiii is atypical species of the genus, and was, in 1851, 

 the only species known in the Jurassics of this country. 



Lingula first made its appearance in the Cambrian period, 

 and has persisted, with slight variations in form, up to the 

 present time ; eight species and three doubtful ones are 

 found in existing seas.* 



LOCALITIES.f 



L. heanii, Phillips, Up. Lias (?), Dundas Aqueduct, near 

 Limpley Stoke, Somerset. 



L. hrodiei, Dav., Coral rag, Wheatley, Oxon. 



L. davidsoni, Oppel, Lower Lias, Grloucester. 



L. Tyietensis, Terquem, Lower Lias, Stonehouse and 

 Churchdown, Grloucestershire. 



* In all instances where the number of living species is given this is 

 stated on the authority of Davidson (11, p. 4). 



t Only those localities -within easy reach of Bristol, or accessible 

 therefrom by cheap excursion trains, will be noted in this paper. 



