256 PALAEONTOLOGY OF NEW YORK. 



allies, Orthis umbraculum* Sclilotheim, and in the Carboniferous by Streptorhynchus 

 lens. White, Spirifer crenistria* Phillips, and others. A noticeable variation from 

 the tvpe of structure described, occurs in the Niagara species, Orthothetes subplanus, 

 where the deltidium of the brachial valve constantly increases in size, from youth 

 onward, while the deltidium of the opposite valve is very slightly developed. 



The term Orthothetes has not come into general use, on account of the want 

 of clearness in its original definition. The species which are now included 

 under it have been generally left with the designation Streptorhynchus, but 

 accepting the views maintained by Dr. Waagen, the latter genus must be re- 

 garded as limited to the Carboniferous and Permian species. Waagen, in 1884, 

 was the first to place Fischer de Waldheim's name, Orthothetes, upon a sub- 

 stantial basis He says: 



"Though this name has been quoted as applied by Evans to certain forms 

 already in the year 1829, yet the genus can not be considered as fairly estab- 

 lished before the year 1830, when in the first edition of the ' Oryctographie,' 

 the interior of a dorsal valve, was distinctly figured and the genus definitely 

 transferred to the Brachiopoda by Fischer de Waldheim. In the edition of 

 1830, only the interior of a dorsal valve was figured, whilst in the edition of 

 1837 an external view of a ventral valve is added. 



" In both cases there can not remain the slightest doubt that the name was 

 applied to a shell very nearly related to Streptorhynchus crenistria, Phill., and 

 which, chiefly in the internal characters of the dorsal valve, is generically 

 identical with Phillips' species."f 



De Waldheim did not apply a specific name to his figured species, and subse- 

 quently, in 1850,J he described two species, Orthothetes radiata and 0. socialis, 

 the former of which has a strong median septum in the pedicle-valve, and 

 both are probably i-eferable to the genus Derbya. De Verneuil identified 

 the figure given by de Waldheim in 1837 § as the Orthis arachnoidea,\\ of 



* The.se species have been recognized by most Ainei-ican authors iis occurring- in the Carboniferous rocks 

 of America. It is <ioublful whethei' a careful comparison of European spei^imens with the American 

 foi-ms will prove them identical. 



t Salt-Range Fossils, 1, vol. iv (fas. 3), p. 607. 



\ Orthothktes ; genre de la Famille des Brachiopodes ; Bull. Society Imp. Naturalistes de Moscou, 

 p. 491, pi. X, tigs. 1-4. 1850. 



§ Oryctographie du Gouvernement de Miiscou, p. 183, pi. xx, tigs. 4, a, b, c. 



I Geologie de la Russie d'Eui'ope et des Montagues de I'Oural, p. Htlj, pi. x, tig. 18 ; pi. xi, tig. 1. 



