WAVEKLY GROUP SPECIES. 281 



I have referred this form to Phillips's species, rather because I have 

 been unable to find any constant characters by which it can be separated 

 from some of the European forms referred to the same by high authori- 

 ties, than from being entirely satisfied that a careful comparison of a 

 large series of specimens might not show it to be a closely allied but dis- 

 tinct species. Although varying in form, it does not, so far as I have 

 been able to see, vary in general outline to the extent that H. crenistria 

 does in Europe, judging from the published figures, nor have I seen any 

 specimens of it with the area so much elevated, or with the beak of the 

 ventral valve so distorted, as in some foreign examples of that shell. It 

 also usually has its posterior lateral portions more compressed and de- 

 flected than if. crenistria, as illustrated from British specimens. 



I see Mr. Davidson, in his very valuable Monograph of the Britsh 

 Carboniferous Brachiopoda, page 124, cites Orthis Keokuk and 0. robusta, 

 Hall, as synonyms of the European species H. crenistria. I can not quite 

 concur with him in this, however, because these, and, I think, all of the 

 several other allied species or varieties found in our Western Carbonifer- 

 ous limestones and Coal Measures differ from the published figures of H. 

 crenistria, as well as from the Waverly sandstone specimens under con- 

 sideration, in having a well-defined, longitudinal mesial septum in the 

 ventral valve, extending from the beak sometimes nearly to the middle 

 of the interior. Mr. Davidson was not acquainted with the interior of 

 Prof. Hall's species, but on examining good specimens of the allied form 

 H. crassa, M. and H., from the Coal Measures, sent by me to him some 

 time back, he noticed this internal septum as distinguishing it from the 

 European species H. crenistria. 



I have, in the Palaeontology of the Upper Missouri, published by the 

 Smithsonian Institution, on pages 25 and 26, given my reasons for be- 

 lieving that the rules of nomenclature will compel us to retain Pander's 

 older name, Hemipronites, for this group, instead of Streptorhynchus, King, 

 whether we regard it as constituting a genus or sub-genus. And in the 

 first volume of the Palaeontology of Ohio, page 73, I have stated reasons 

 for believing that when the interior of all of the Carboniferous, Devon- 

 ian, and Silurian shells of this and allied groups can be thoroughly com- 

 pared, it will be seen that Hemipronites is so closely related to Strophomena, 

 Rafinesque, that it can scarcely be separated from the latter more than 

 as a sub-genus. Prof. King's name was proposed for Permian species, 

 with the area and beak of the ventral valve extravagantly elevated, and 

 the beak often much distorted ; but when we pass to some of the Carbon- 

 iferous, Devonian, and particularly to the Silurian species, we find ex- 

 amples with the area nearly or quite as little developed as in some 



