178 
PALAEONTOLOGY OF NEW YORK. 
upon the apical substance of the valve. Persistence of any of these conditions 
at maturity may be of collateral value in determining the subdivisions of these 
fossils, but it is impossible to base important values upon them. It is indeed 
uncertain whether the authors of the names above mentioned had before them 
species of Rhynchonella, and those terms must necessarily be rejected. 
The first inquiries before us are; What is Rhynchonella in its strict signi¬ 
fication ? and, How far is it represented in palaeozoic faunas ? 
Genus RHYNCHONELLA, sensu stricto. 
PLATE LVI. 
* 1809. Rhynclionella, Fischer de Waldheim. Notice des Fossiles du Gouv. de Moscou, p. 35, pi. ii, 
figs. 5, 6. 
1827. Rhynclionella, de Blainville. Diet, des Sciences Naturelles, vol. xlv, p. 426. 
1837. Rhynchonella, Fischer de Waldheim. Oryctogr. du Gouv. de Moscou, pi. xxiv. 
1853. Rhynchonella, Davidson. Introd. British Fossil Brachiopoda, pi. vii, fig. 99. 
1856. Rhynchonella, Suess. Classif. der Brachiopoden voii Th. Davidson, pi. iv, fig. 1. 
1871. Rhynchonella, Quenstedt. Petrefactenkunde Deutschlands; Brachiopoden, pi. xxxviii, fig. 108. 
1880. Rhynchonella, Zittel. Handb. der Paliiontologie, p. 689, figs. 529 a-d. 
Subpyramidal shells having the margins of the valves sinuous or angulated. 
Pedicle-valve with a median sinus beginning in front of the convex umbo, and 
in the type-species, becoming broad and deep, producing a prominent lingui- 
form extension at the anterior margin. Brachial valve convex in the umbonal 
region and developing anteriorly a prominent median fold. Surface of both 
valves more or less plicated, often accompanied (as in the type) by fine con¬ 
centric lines of ornament. The apex of the pedicle-valve is but slightly 
incurved and exposes a circular or elongate-oval foramen enclosed by deltidial 
plates beneath, and above by the substance of the valve. There is a narrow 
pseudo-area defined by oblique cardinal ridges diverging from the beak. On 
the interior the teeth are well developed and are supported by lamellae which 
rest on the bottom of the valve near the beak, but are free anteriorly. The 
muscular area consists of a moderately deep oval scar extending one-third the 
length of the valve, and composed of two large diductors completely enclosing 
* The citations here given refer only to Rhynchonella loxia. Accounts of congeneric Jurassic species 
will be found in the works of Davidson, Fischer de Waldheim, Sowerby, d’Archiac and de Verneuil. 
