298 
PALAEONTOLOGY OF NEW YORK. 
No author has been in a more favorable position for the study of Pander’s spe¬ 
cies than M. de Verneuil, and his testimony is of much 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. transversalis 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 Plectambonites. f 
Genus CHRISTIANIA 4 gen. nov. 
PLATE XV, FIGS. 32, 33; AND PLATE XVa, FIG. 36. 
1887. Plectambonites, Pander. Beitr. zur Geognosie d. russ. Reiches, p. 92, pi. xix, figs.. 9, 10. 
1840. Orthis, von Eichwald. Ueber das Silur. Schicht. Syst. in Estland, p. 148. 
1845. Leptcena, de Verneuil. Geol. de la Russ, et des Mont, de l’Oural, p. 228, pi. xv, fig. 2. 
1846. Productus, McCoy. Synopsis Silurian Fossils of Ireland, p. 25, pi. iii, fig. 4. 
1858. Leptcena, Davidson. Introd. British Fossil Brachiopoda, pi. viii, figs. 184, 185. 
1871. Leptcena, Davidson. British Silurian Brachiopoda, p. 826, pi. xlvii, figs. 7-18. 
1S83. Leptcena, Davidson. British Silurian Brachiopoda, Suppl., p. 168, pi. xii, figs. 17-21. 
1S83. Leptcena, Hall. Rept. IN'. Y. State Geologist for 1882, Expl. pi. xv (46), figs. 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 Orthis de l’Esthonie. Parmi les Plectambonites de M. Pander, il y en a 
quatre qui ont une extreme ressemblence aux l’espece dont nous nous occupons. Les Plectambonites planis- 
sima et crass a sont ceux que nous aurions voulu choisir comme types, mais ces deux noms ayant deja 6te 
donnes a des Orthis ou a des Atrypa, nous preferons adopter le nom de convexa qui n’a pas encore ete em¬ 
ploye.” 
* The species Leptcena sordida and L. decipiens, described by Mr. Billings, from the Levis formation, 
prove to be genefically distinct, and are discussed under the genus Leptella. 
t See the more recent determinations by Munier de Chalmas, Bittner, Zugmayer, and others. The 
first of these authors has established the genera Koninckella (type. Leptcena liasina, Bouchard) and Cad- 
omella (type, Leptcena Mocrrei, Davidson), for some of the Liassic species. 
I This name is proposed as an expression of regard for the memory of Dr. Christian Heinrich Pander. 
