THE ANNALS 



AND 



MAGAZINE or NATURAL HISTOEY. 



[SEVENTH SERIES.] 

 No. 84. DECEMBER 1904. 



LIT. — Jurassic Bracliiopoda. By S. S. BuCKMAN, F.G.S. 



It is hoped tliat the following notes on certain genera and 

 species of Jurassic Bracliiopoda may be of service in regard 

 to some technical points of nomenclature. Several of them 

 are the result of investigations nndertaken to ascertain what 

 were the correct descriptions by which certain species in the 

 collection at the British Museum (Natural History) should 

 be classified. Such investigations are too often of a snowball 

 character — the revision of nomenclature in one case opening 

 a wider and wider field of inquiry. 



Genus — OiiTiiOTOMA, Quenstedt, 1871. 



As the genotype Quenstedt names Terehratula heyseana ; 

 but what he figures under this name is not the same species as 

 that figured by Dnnker. Tiierefore Terehratula heyseana^ 

 Quenstedt (non Dunker), is properly the genotype of 

 Ortliotoma, and what this is may be seen from Handbuch 

 Petref. 1851, pi. xxxvii. fig. 47, to which he refers. 



The external characters of the genus Ortliotoma are sharp 

 beak-ridges, small foramen, and a tendency to sulcate the 

 dorsal valve, while showing through the test should be the 

 mark of a short septum. Tlie dorsal sulcus is not always 

 found in the later species, 0, anglica; it is often seen in 



Ann. & May. N. Hist. Ser. 7. Vol. xiv. 28 



