CONTRIBUTIONS TO PALEONTOLOGY. 309 



VIIL REMARKS UPON THE GENERA RHYNCHONELLA AND LEIORHYNCHUS. 



In the fourth volume of the Palceontology of New YoyJc, pages 332-4, 

 under the Genus Rhtnchonella of Fischer, I have made the following 

 remarks : 



" The species RJnjnchonella loxia is made the type of this genus by its 

 author. It is ouly withiu a recent period that the name has been so extensively 

 applied to nearly all the ovoid or subtrigonal plicated, and some smooth shells 

 of all geological epochs, from Lower Silurian to the most recent formations, 

 and it has been recognized in two existing species. 



"In the Introduction to the Study of the Brachiopoda (page 95 of the English 

 edition, page 117 of the French edition), Mr. Davidson remarks : 'The Genus 

 Ehtnchonella is one of the oldest tj'pes of animal life, having been repeated 

 from the Silurian epoch up to the present period ; two species are still found 

 alive.' 



"I have heretofore accepted the general views of palaeontologists regarding 

 this genus, and have described a number of species under it; but I have long 

 been satisfied that, in malting such extensive application of the term Rhyncho- 

 NELLA, we are in danger of falling into an error of scarcely less magnitude 

 than that of referring all similar forms, with many others, to the Genus Tere- 



BEATULA. 



" Unfortunately the internal characters of R. loxia do not seem to be known ; 

 at least I have not seen them illustrated ; and though cited as the type by 

 Mr. Davidson, and figured upon the plate, it is not enumerated in his list of 

 eighteen examples. Mr. Woodward gives as types R. acuta, furcellata, sjpinosa, 

 acuminata, nigrescens and psittacea — species enumerated in Mr. Davidson's 

 list — but he does not cite R. loxia. 



" With the interior structure of the type of the genus unknown, while the 

 parts are illustrated from recent species, or from fossil ones supposed to belong 

 to the genus, we are not likely to make satisfactory progress in the arrangement 

 of the fossils usually referred to it. A careful study of those fossils which 

 have been cited as examples of genera, passing through all the geological stasjes 

 and still existing, has proved, in some of them at least, that the assumption was 

 not well founded ; and I think we should hold such views with reservation. 

 In the present instance I must be allowed to doubt whether R. loxia will be 

 found to possess the characters of Lower Silurian and of existing Ehynchonelte ; 

 nor do I consider the characters of the existing species as congeneric with those 

 of the older Silurian or Devonian formations. The necessity felt for some other 

 designation to apply to some of these forms has induced the names Hypothyris, 

 Hemithyris, Cyclothyeis, etc. ; but these do not appear to have been founded 

 on reliable structural characters. That some subdivision will become necessary, 



