254 
PALEONTOLOGY OF NEW YORK. 
vidual. With age it became filled up by adventitious deposits. The crura are 
long, straight, inclining upward or toward the opposite valve and are expanded 
at their extremities into palmate processes. The muscular scars in this valve 
are sharply developed, forming together an elongate adductor area, clearly 
divisible into an attenuate anterior pair and a broader posterior pair. The 
former have about twice the length of the latter and are marked by trans¬ 
verse, fine, closely-set wrinkles; the latter are radiately and coarsely striate. 
From the posterior termination of this area to beneath the hinge-plate extends 
a broad, smooth sinus, from which is given off a pair of strong lateral branches, 
which ramify over the genital area in the umbonal region. Thus, except in the 
character of its crural processes, the structure of the brachial valve and the 
indications in regard to the composition of the muscular system are identical 
with those of RensspMria ovoides. 
As already observed, the specific type of Amphigenia elongata varies little, if 
at all, during the existence of the genus. A. elongata, var. curia, was described 
by Meek and Worthen, from the beds at Jonesboro, Ill., which have been 
regarded as of the age of the Oriskany sandstone of New York, though con¬ 
taining a number of Upper Helderberg types. Similarly, A. elongata has been 
reported by Billings from the Oriskany fauna of Cayuga, Ontario, in which 
there is even a larger representation of Upper Helderberg species. In the 
New York faunas it appeared first in the Schoharie grit, where it is not com¬ 
mon. In the Corniferous limestone it abounds in certain localities, especially 
in the western part of the state, and with the close of the Upper Helderberg 
it disappears. 
The occurrence of fine, large and typical examples of the species in the 
lower Devonian sandstones of the rivers Msecuru and Curml, Province of 
Pani, Brazil, has been noted by Bathbun {loc. cit.). 
(Ehlert has described as Amphigenia ? Bureaui, a large shell with smooth 
exterior and small spondylium in the pedicle-valve, resting on the bottom of 
the valve and not supported by a septum, as in A. elongata. This shell is from 
the lower or middle Devonian of Montjean and Challones (Maine-et-Loire), 
France. 
