186 PALEONTOLOGY OF NEW YORK. 



ratus on the one hand, and the obsolescence of other characters, which appear 

 in the earlier forms of strophomenoid shells and have become modified in their 

 progress through the chonetids. This may in one aspect be regarded as a 

 degeneration, while in another it is apparently a development or progress, and 

 affords no sufficient reason for beginning at the end of a series and going 

 backward. 



Of the various designations which have been proposed with a signification 

 equivalent to Professor Huxley's term* for this subdivision of the Brachiopoda, 

 are Arthropomata, OwEN,f Clistenterata, King;J while Bronn§ made use of 

 the two names Testicardines and Apygia. 



No attempt is here made toward any grouping of the genera into the 

 numerous families or sub-families which have been proposed by different 

 authors. In this division, as in the Brachiopoda Inarticulata, our knowledge 

 has so greatly increased in the past years that such a classification if attempted 

 must be arbitrary and procrustean, and would only be embarrassing to the 

 student without any corresponding benefit. The interrelations of these genera 

 will be better understood from the discussions under each one, and will be 

 briefly summarized in a concluding chapter. 



Genus ORTHIS, Dalman. 1828. 



I'LATES V, Va, Vb, Vc. VI, VIA. 



Hyaterolitlnis (partim), of Aldrovandus (1648) and other pi-ffi-Linnean authoi-s. 

 1820. Hysterolithes (partim), Schlotheim. Die Petrefactenk. auf ihr. jetzig-. Standpunkt. 

 IS'JS. Ortliis, Dalman. Kongl. Svenska Vetenskaps-Akad. Handl. for 1827, pp. 93, 96; pis. i, ii. 

 1830. Orthambonites, Poramhonites {partim). Pander. Beitr. zur Geogn. des russisch. Reiches, 



pp. SO, 95. 



Delthyrls, Spirifer, Productiis, Terehratula of some early authors. 



Orthis of authors genei'ally. 

 1838. OrtHs, Conrad. Second Annual Rept. N. Y. Geol. Survey, pp. 112, 118. 

 1842. Orthis, Terehratula. Spinfer, D'Orbigny. Voyage dans I'Amerique meridionale, Paleontologie, 



pp. 27, 38, 39, 48. 

 1842. Orthis, Delthyrls, Emmons. Geology of N. Y. ; Rept. Second Dist., pp. 394, 396, 404. 

 1842. Orthis, Vancxbm. Geology of N. Y. ; Rept. Third Dist., pp. 139, 140, 163, 164. 



* An Introduction to the Classification of Animals, ji. 116. 1869. 

 t Encyclopaedia Britannica, 8th ed., vol. xv, p. 336. 1858. 

 X Annals and Magazine of Natural History, vol. xii, p. 15. 1873. 

 § Die Classen und Oi-dnungen des Thierreichs, p. 301. 1862. 



