196 PALAEONTOLOGY OF NEW YORK. 



Unci7udu.<!, Bayle. Explic. <le la Carte gi'olog. France, vol. iv, Atlas, pi. xi, figs. 17-20. 

 Unclnulhia, Baylk. Explic. de la Carte geolog. Finance, vol. iv, Atlas, pi. xiii, tigs. 13-16. 

 JRkynclionella, Bahri.s. Proc. Davenport Acad. Nat. Sci., vol ii, p. 285. pi. xi, tigs. 5, 6. 

 Rhynchonella, Hall. Twenty-eighth Ann. Rept. N. Y. State Mus. Nat. Hist., p. 165, pi. xxvi, 



tigs. 34-40. 

 Uncinulus, Waac.en. Salt-Range Fossils, Braihiopoda, p. 424. 

 Rhynt-honella, Davidson. Brit. Silur. Brachiopoda ; Suppl., p. 156. 

 Uncimdits, CEhlekt. Bull, de la Soc. g6ol. <le France, 3d ser., vol. xii, pp. 426-432, jil. xxi, 



figs, las ; pi. xxii, figs. 2 a-n. 

 (4) 1884. Rhynchonella, Walcott. Monogr. U. S. Geol. Snrv.. vol. viii, p. 157. 



(3) 1884. Rhynchonella, CEiilert. Bull, de la Soc. geol. de Fi-ance, 3d ser., vol. xii, p. 420, pi. xviii, 



fig. 5a-o. 



(4) 1884. Rhynchonella, Clarke. Neues Jahrb. fiir Mineral., Beilagebnd. iii, p. 385. 



(4) 1890. Rhynchonella, Williams. Bull. Geol. Soc. America, vol. i, pp. 481-500, pis. xi, xiii. 

 (4) 1891. Rhynchonella, Clarke. Ainei-ican Geologist, August, p. 100. 



There are large numbers of palaeozoic rhynchonellas which are characterized 

 by a full subcuboidal or subpentahedral contour, a fold and sinus not sharply 

 developed except at the anterior margin, an abrupt anterior slope, sharply ser- 

 rated lateral margins of contact, and low .surface plications, each of which, on 

 the front of both valves, is marked by a fine median line. 



Shells with sucli external features appeared in the middle or upper Silurian, 

 midtiplied in the early Devonian, and continued their existence into the faunas 

 of the Carboniferous. They were early distinguished as the group of Rhyncho- 

 nella Wilsoni, Sowerby, taking their name from the common species of the 

 Wenlock fauna, which was quite fully described and illustrated by Davidson in 

 the Annals and Magazine of Natural History, 1852,* and still more elaborately 

 in his Silurian Brachiopoda, 1869.f In 1871, QoenstedtJ termed the shells 

 "die Wilsonier" or "the Wilsoni's," introducing for them a trinomial nomen- 

 clature, as, for example, R. Wilsoni Bohemica, R. Wilsoni pila, etc., etc. 



That this term was not intended as a generic or subgeneric designation is 

 evident from its mode of use, but in the same year Professor E. Kayser, § in 

 referring to Quenstedt's recently expressed opinion, says that " the characters 

 [mentioned] seemed to him [Quenstedt] sufficient for the establishment of 

 a separate subgenus " Wilsonia," Thus the name Wilsonia was introduced, 



* p. 249, pi. xiii, figs. 12-14. 



t P. 168, pi. xxiii, figs. 1-18. 



I Petrefactenkunde Deutschlamls ; Brachiopoden, p. 193. 



5 Zeitschrift der deutsch. geolog. Gesellsch., vol. xxiii, p. 502. 



