236 
PALAEONTOLOGY OF NEW YORK. 
It was evidently the intention of the author to make not only these two 
divisions Pronites and Hemipronites of the genus Klitambonites, but also to 
include as of coequal value the divisions GonA.mbonites, Orthambonites and 
Plectambonites ; and the principal differences in these divisions, as based on 
the varying inclination of the cardinal area, are expressed in the following 
figures taken from Plate 28 of his work. 
After Pander. 
Orthambonites is undoubtedly precisely synonymous with Orthis, Dalman. 
Plectambonites is manifestly a good genus, equivalent to Lept^ena of authors, 
not of Dalman. Dall has called attention* to the fact that Pander, in sub¬ 
dividing the entire group of Clitambonites, left no type-species upon which the 
shaped, sometimes triangular opening for the passage of the fleshy pedicle. The . four sides of the shells 
are most clearly pronounced; the surfaces are slightly arched, that of the upper valve usually sloping from 
the apex of the cardinal area, which is generally the highest point, rather abruptly forward, and more gently 
toward the sides. The transverse diameter is usually the greatest. 
“The fine longitudinal ribs are interrupted by concentric lines, parallel to one another and to the ante¬ 
rior and lateral margins ; thus the former lie on one another like steps or roof-tiles. The anterior margin 
is, in general, straight, rarely, and then but inconsiderably, bending toward the upper valves. As, however, 
there are great differences both in convexity and in the diameter and height of the cardinal area, it will 
be more convenient to separate the Klitambonites into two divisions, which are distinguished principally by 
the fact that in one, which we term Pronites, the upper angle of the triangular cardinal area reaches the 
highest point in the shell, while in the Hemipronites, the last lies between the posterior and anterior mar¬ 
gins, and the cardinal area is therefore lower.” 
♦Bulletin No. 8, U. S. National Museum, p. 39. 1877. 
