298 PAL/EONTOLOGY OF NEW YORK. 



No author has been in a more favorable position for the study of Pander's spe- 

 cies than M. de Verneoil, and his testimony is of mucli accessory importance in de- 

 termining the real import of the genus Plectambonites. That he himself did not 

 adopt the generic term, is due to the fact that he followed the prevailing custom 

 of rendering to a genus the full breadth of meaning given to it by its author. 



The elongate-lobate muscular scars, and the peculiar structure of the cardi- 

 nal process are features which at once distinguish Plectambonites from allied 

 genera. The former character is sometimes approached in certain species of 

 Rafinesquina. Species of this genus have probably not appeared earlier than 

 the faunas of the Trenton and Caradoc-Bala* 



The genus disappears in the Niagara; P. transversaUs being the last survivor 

 represented. It has been quite generally believed that the genus reappeared 

 in the Trias and Jura, but many of these species have already proven to be of 

 a distinct type of structure, and all of them will unquestionably be found to 

 differ essentially from PLECTAMBONiXES.f 



Genus C H Pv I S T I A N I A,^ gen. nov. 



PLATE XV, FIGS. 32, Si; AND PLATE XVa, FIG. in. 



1837. Plictnmbonitea, Pander. Beitr. ziir Geog'nosie d. russ. Reiche.s p. 92, pL xix, tiys. 9, 10. 



1840. Orthis, von Eichwald. Ueber das Silur. Schicht. Syst. in Estlaiid, p. 148. 



1845. LeptcBmi, db Verneuil. GeoL de la Russ. et des Mont, de rOural, p. 228, pi. xv, i\g. 2. 



184(). PmdurtiL'), McCoy. Syniipsis Silurian Fossils of Ireland, p. 25, pi. iii, fig. 4. 



ISii'i. Lept(Btta, Davidson. Introd. Biitish Fossil Brachiopoda, pi. viii, tigs. 184, 185. 



1871. LeptcBna, Davidson. British Silurian Brachiopoda, p. 320, pi. xlvii, figs. 7-lS. 



ISS3. Lepkena, Davidson. Bi-itish Silurian Brachiopoda, SuppL, p. 168, pi. xii, tigs. 17-21. 



1S83. LepUeiM, Hall. Kept. N. Y. State Geologist for 1882. Expl. pi. xv (4G), tigs. 32. 33. 



Diagnosis. Shells usually longitudinally elongated, sometimes semielliptical in 

 outline ; normally concavo-convex. Surface smooth or covered with fine radiat- 



ete applique par M. Eichwald a une OrthU de I'Esthonie. Parmi les Plectambonites de M. Pander, il y en a 

 quati'e qui out une extreme ressemlileiice aux I'espece dont nous nous occupons Les Pleidambonltes planLt- 

 siiiM et wassa sont ceux que nous aurions voulu choisii- connne typos, mais ces deux noms ayant deja 6te 

 donnes a des Orthis on a des Atrypa, nous preferons adopter le nom de convexa qui n'a pas encore ete em- 

 ploye." 



* The species Leptmn.a sardida and L. declpietut, described by Mr. Billings, from the Levis foi-matiou, 

 prove to be generically distinct, and are di.scusseil under the geiuis Leptblla. 



t See the more recent detiu-miuations liy Mlniku de Chalmas, Bittnek, Zugmavku, and others. The 

 tir.st of tlii'se author.s lijis estalitished the genera Koninckklla (type, Li'.piOBMi llnnmit, Bou<-liard) and (^ad- 

 omklla (type, LeplcBna Monrei, Davidson), fm- some of the Liassic species. 



% This name is proposed as an expression of regard for the memory <if Dr. Chkistian HKi.MiicH Pander. 



