198 
PALEONTOLOGY OF NEW YORK. 
On the other hand, the Devonian species, R. sub-Wilsoni, d’Orbigny, possesses a 
solid, undivided hinge-plate and a highly developed cardinal process, as was 
shown by Davidson, in 1852, and by (Ehlert, in 1884; and though having ex¬ 
ternal contour, median septum and unsupported teeth, as in R. Wilsoni, should 
not be placed in too intimate association with the latter. The generic charac¬ 
ters of R. suhwilsoni are positive, those of R. Wilsoni are unsubstantial. If 
WiLSONiA has any value as a distinctive designation it is subordinate to Cama- 
ROTCECHiA, and as such may serve to characterize the subcuboidal shells of this 
group which, like R. Barrandii, Hall, and the species constituting the proposed 
subgenus Plethorhynchus, have the teeth unsupported by dental lamellae. To 
adopt the name Wilsonia for all the shells possessing the internal characters of 
R. Wilsoni, without regard to external form, and thus make it the equivalent of 
the group Camarotcechia, would be to deviate widely from the intent of the 
authors of the term; hence, per contra, it becomes necessary to restrict the 
application of the name to very narrow limits. 
In American faunas the typical Wilsonia is but sparsely represented. With 
it may be placed the species R. Saffordi, Hall, to which reference has been made. 
Perhaps the R. ventricosa, Hall, of the Lower Helderberg fauna (Shaly lime¬ 
stone), a shell referred to in the discussion of Camarotcechia, should be associ¬ 
ated with it. Rhynchomlla Wilsoni is a species of wide distribution in the 
European Upper Silurian, and has been described in Great Britain, Sweden, 
Russia and Spain; Davidson gave its vertical range as from the Llandovery to 
the Ludlow periods. It is probably true that the very few other species of 
similar type of exterior, which have been described from the Wenlock and 
equivalent faunas, are congeneric, but this statement can be made only with 
reservation, 
Bayle, in 1878, proposed* to use the term Uncinulina for a species described 
by him as Uncinulina fallaciosa, from the lower Devonian of Nehou and else¬ 
where, To Dr. CEhlert, again, we owe the elaboration of this shell, f The 
species is subcuboidal in form, less globose than R. Wilsoni, but with the abrupt 
* Exi^lication Carte geolog:. France, Atlas, pi. xiii, figs. 13-16. 
t Op. ait., p. 420, pi. xviii, figs. 5a-o. 1884. 
