216 
PALAEONTOLOGY OF NEW YORK. 
Genus SYNTROPHIA,* gen. nov. 
PLATE LXII. 
1861. Camarella, Billings. Canadian Naturalist and Geologist, vol. vi, p. 318. 
1862. StricTilandiniaf, Billings. Palseozoic Fossils, vol. i, p. 85, figs. 77, 78. 
1864. Oithis, A. Winchbll. American Journal of Science, second series, vol. xxxvii, p. 229. 
1882. LeptWna, Triplesia, Whitfield. Geology of Wisconsin, vol iv, p. 171, pi. i, figs. 6, 7 ; pi. iii, fig. 6 ; 
p. 172, pi. X, figs. 1, 2. 
1886. Triplesia, Whitfield. Bull. American Mus. Naf. Hist., vol. i. No. 8, p. 303, pi. xxiv, figs. 9-11. 
1892. SyntropMa, Hall. Palaeontology of N. Y., vol. viii, part i, p. 270. 
In considering the spondylium-bearing shells of the earlier faunas, there are 
great difficulties in the determination of positive taxonomic characters. The 
features of the exterior and, to a great degree, those of the interior, are plastic 
and variable, failing to assume that fixity of form possessed by their successors 
in later faunas, and upon which we depend for a proper conception of generic 
values. Here circumspection must be used, lest generic distinctions be too 
arbitrary, or too narrowly drawn on the basis of differences which, among 
later fossils, would properly be considered of higher significance. The earlier 
divisions must be allowed more elasticity, as the types they include are forma¬ 
tive and inconstant. The spondylium-bearing species of the Lower Silurian 
are mostly subtrihedral shells with the external aspect of Rhynchonella, but 
there are a few described species which have an exterior similar to members of 
the genera Protorthis and Billingsella, that is, they are small, transversely 
elongate in outline, with straight, well-defined cardinal area. Such are the 
Stricklandinia ? Arachne and S. Arethusa, Billings, of the Quebec group (Lime¬ 
stone No. 2); Orthis Barahuensis, A. Winchell, from the Potsdam sandstone of 
Baraboo, Wisconsin, and the Triplesia lateralis, Whitfield, of the Calciferous 
fauna of New York and Vermont. For these shells the name Syntrophia will 
be adopted, the last-named species being selected as the type of the group, 
since the material derived from various sources has afforded the means of 
obtaining a very clear conception of its external and internal features. 
“ The Triplesia lateralis, Whitfiehl, of the Fort Cassin beds (Calciferous sandstone), contains a spoon-shaped 
process in each valve, that in the pedicle-valve being suppoi'ted by a median septum. It therefore becomes 
necessary to remove this form to a distinct genus and to a different association, and it will be described and 
illustrated in its proper place under the name Syntrophia.” —Palieontology of New York, vol. viii, part i, 
page 270. (This note was printed in 1891.) 
