GENERA RHYNCIIONELLA AND LEIORHYNCHUS. 2G9 



IX. REMARKS UPON THE GENERA RHYNCIIONELLA AND 



LEIORHYNCHUS. 



In the Fourth volume of the Palaeontology of New- York, pages 332-4, 

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

 remarks. 



' The species Rhyjichonella loxia is made the type of this genus by its 

 author. It is only within a recent period that the name has been so exten- 

 sively 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 Rhynchonella is one of the oldest types 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 paloeontologists regard- 

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

 have long been satisfied that in making such extensive application of the 

 term Khynchonella, we were in danger of falling into an error of 

 scarcely less magnitude than that of referring all similar forms, with many 

 others, to the Genus Terebratula. 



' 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, 

 furcellat.a, spinosa, acuminata, nigTcscens and psittacea ; species enume- 

 rated 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 stages 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 Khynchonella ; 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 desig- 

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

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

 founded on reliable structural characters. That some subdivision will 

 become necessary, and will be adopted, I have no doubt ; but such a 



