186 PALAEONTOLOGY OF NEW YORK. 



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

 in the earlier forms of sirophomenoid 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 tlie various designations which have been proposed with a signification 

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

 are ARTiiRoroMATA, 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. 



PLATES V, Va, Ve, Vc. VI, VIa. 



HysteroHthiis (partim), of Aldrovandus (lt)48) ami other pi-ffi-Liniiean authoi-s. 

 1820. HystevoUUies (jmrthn), Schlotuetm. Die Pi^trefju-tenk. auf ihr. jetzig-. Stamlpuiikt. 

 IS'28. Orthis, Dalman. Kongl. Svenska Vetens^kaps-Akail. Handl. for 1827, \f\t. 98, 96; pis. i, ii. 

 1830. Orlhamhonites, Porambonites (partim). Pander. Beitr. zur Geogn. des russisch. Reiches, 



pp. 80, 9.5. 



Delthyris, Spirifer, Productus, Terebratula of .some eai-ly authors. 



Orlhis of author.s g-enerally. 

 1838. Or/;n.s-, Conrad. Second Annual Kept. N. Y. (thoI. Survey, pp. 112, 118. 

 1842. Orthis, Tereln'atula. /Spirifer, D'ORniGNV. Voyage dans rAmeriquo rnei'idioiiale, Paleontologie, 



pp. 27, 38, 39, 48. 

 1842. OHMs, Delthyris, Emmons. Geology of N. Y. ; Kept. Second Di.st., pp. 394, 396, 404. 

 1S42. OrtJiis, Vancxem. Geology of N. Y. ; Kept. Third Dist., pp. 139, 140, 163, 164. 



* An Introduction to the Classitication of Animals, p. 116. 1869. 

 t Encyclopffidia Britannica, Sth ed., vol. xv, p. 336. 1858. 

 J AiinaKs and Magazine of Natural History, vol. xii, p. 15. 1873. 

 5 Die Cla-ssen und Ordnungen des Thierreichs, p. 301. 1862. 



