Williams. j THE GENUS CAMARO AECH1A. 5 ( J 
Orthorhynchula and Rhynchotreta are so far differentiated from the 
dominant characters of the rhynchonellids that they may be omitted 
from the present treatment as reaching their full specialization in the 
Niagara, and not having direct descendants in the later formations. 
The genus Rhynchonella, although strictly speaking having no rep- 
resentatives in the Paleozoic, is still left for the reception of all the 
species whose characters are not sufficiently well differentiated from 
the general family characters of the Rhynchonellidae to have furnished 
any specialist the means of erecting a new group for them. It is quite 
possible that the Maine rhynchonellas described as R. aspasia by Bil- 
lings were descended from some one of these earlier rhynchonellas 
not }^et separated into special (literary) groups. The other group, 
Uncinulus Bayle, into which a large majority of Lower Helderberg 
species falls, has for its possible ancestors species of Wilsonia, Cam- 
arotoechia, and the remnant, not distributed, of Rhynchonella. 
CAMAROTCECHIA Hall. 
According to the definitions grouped under this name, the distinctive 
characters by which it is marked seem to be: (1) The absence of a car- 
dinal process; (2) a median septum in the brachial valve, so divided as 
to make a cavity between the teeth before reaching the outer wall of 
the shell. On these grounds Hall and Clarke include R. ventricosa in 
Camarotoechia, but they distribute all the other rhynchonellas in other 
subdivisions. In their final revision of the Brachiopoda these authors 
state that "the structure of Camarotoechia is possessed by the extrava- 
gantly gibbous species R. ventricosa." 1 The forms of the Lower 
Helderberg most closely related to those called Camarotoechia below 
and above that horizon are distributed in another group, called Uncin- 
ulus, and the three characteristic rhynchonellas of the Oriskany are 
again gathered into the Camarotoechia group. 
This omission of the camarotoechias, except the one species, from the 
Lower Helderberg faunas is explained by these authors as follows: 
At the appearance of the Lower Helderberg faunas, with their multiplicity of 
rhynchonellids, this type of structure appears to have yielded somewhat to the 
robust forms possessing a cardinal process which are referred to the genus Uncinulus. 1 
It has already been stated that the Lower Helderberg fauna is 
remarkable for the abundance of the rhynchonellas of the Uncinulus 
type. These forms in all their superficial characters seem to be in 
the line of passage from the rhynchonellas, called Camarotoechia, 
below and above the Lower Helderberg. It is difficult for one accus- 
tomed to recognize genetic affinity in successive faunas not to regard 
the forms of Uncinulus of this period as the direct descendants of 
rhynchonellas of the Camarotoechia and Wilsonia type in. the earlier 
iPal. New York, Vol. VIII, Pt. II, p. 191. n - Op.cit., pp. 190-191. 
