186 
PALAEONTOLOGY 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,| 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. 
PLATES V, VA, Vb, VC. VI, VIA. 
Hysterolithus (partim), of Aldrovandus (1648) and other prae-Linnean authors. 
1820. Hysterolithes (■partim), Schlotheim. Die Petrefactenk. auf ihr. jetzig. Standpunkt. 
1S28. Orthis, Dalman. Kongl. Svenska Vetenskaps-Akad. Handl. for 1827, pp. 93, 96; pis. i, ii. 
1830. Orthambonites, Porambonites (partim), Pander. Beitr. zur Geogn. des russisch. Reiches, 
pp. SO, 95. 
Delthyris, Spirifer, Productus, Terebratula of some early authors. 
Orthis of authors generally. 
1838. Orthis, Conrad ; Second Annual Rept. N. Y. Geol. Survey, pp. 112, 118. 
1842. Orthis, Terebratula. Spirifer, D’Orbigny. Voyage dans l’Amerique meridionale, Paleontologie, 
pp. 27, 38, 39, 48. 
1842. Orthis, Delthyris, Emmons. Geology of N. Y.; Rept. Second Dist., pp. 394, 396, 404. 
1842. Orthis, Vancxem. Geology of N. Y.; Rept. Third Dist., pp. 139, 140, 163, 164. 
* An Introduction to the Classification of Animals, p. 116. 1869. 
t Encyclopaedia Britannica, 8th ed., vol. xv, p. 336. 1858. 
I Annals and Magazine of Natural History, vol. xii, p. 15. 1873. 
§ Die Classen und Ordnungen des Thierreichs, p. 301. 1862. 
