288 
PALAEONTOLOGY OF NEW YORK, 
The whole structure is very similar to the brachidium of the adult living 
Magellania (Waldheimia)."^ 
The adductor scars are more or less distinct, the anterior members being the 
more clearly defined. These scars are usually represented only by three straight 
lines diverging from the umbonal region. Vascular sinuses originate about the 
muscular areas of both valves and are directed forward with frequent rami¬ 
fications. 
The shell-structure is highly punctate. 
It thus appears that the Devonian shells which can be referred to Crypto- 
NELLA do not materially differ in the structure of the brachidium from the living 
Magellania. There are several species in the American faunas, currently 
referred to this genus, whose brachidia have not yet been developed, e. g., 
C. eximia, Hall, of the Lower Helderberg, C. Iphis, Hall, of the Upper Helder- 
berg, and C. Eudora, Hall, of the Chemung, but in all these the probability of 
their being congeneric with C. rectirostra, is enhanced by the demonstration of 
the absence of the transverse dorsal band on the brachidium of the latter. 
From Davidson’s determinations we know that the same type of brachidium 
existed in the Devonian faunas of Great Britain, Waldheimia juvenis, Sowerby 
(sp.), and W. Whidbornii, Davidson,f both shells with smooth exterior, the latter 
with biconvex valves, the former with a plano-convex or centronellid contour. 
From certain preparations made by Dr. Carl Rominger, in 1863,| it was deter¬ 
mined that the Terebratula or Retzia melonica, Barrande, from the Bohemian 
Etage F .2 (Konieprusian), possesses a brachidium of the same type. This is a 
large biconvex shell quite different in expression from the diminutive navicu- 
* III the description and illlustrations of 1867 the brachidium was represented as possessing’ a trans¬ 
verse band on the dorsal side, uniting the descending branches at points just below, and slightly back of 
the position of the ci’ural apophyses. Such a transverse band does not exist. In making preparations 
of these internal parts slight ineptitude will divide the long concave hinge-plate in such a manner that 
its anterior edge remains attached to the crura. Repeated attempts with the knife have almost invariably 
given this I’esult, but certain specimens in which the entire brachidium has been changed to pyrites 
have determined the inaccuracy of such preparations and the absence of this abnormal structure. 
t Devonian Supplement, 1882, pp. 12, 13, pi. i, figs. 1-4. 
I Sixteenth Report on New York State Cabinet of Natural History, p. 49, figs. 24-26. See also Bar- 
RANDB, Syst^me Silurien, vol. v, pi. cxli. 1879. 
