230 
PALEONTOLOGY OF NEW YORK. 
Genus LYCOPHORIA, Lahusen. 1885. 
PLATE LXIII. 
This name has been proposed for the Atrypa nucella, Dalman, a species not 
unlike Porambonites in general external features. The valves are rotund and 
have neither fold nor sinus, so that the anterior margin of contact is almost 
straight or very gently sinuous. The beaks are full and closely incurved and 
only the pedicle-valve appears to have retained a foramen, though the cardinal 
area is present in both. The brachial valve bears a hinge-plate which is 
recurved into the pedicle-cavity of the opposite valve and is produced into a 
long, curved cardinal process, bifurcate at its extremity. The crural plates 
are connected with the elevated margins of the four adductor impressions. In 
the opposite valve the teeth are supported by divergent plates which extend 
forward for about one-half the length of the shell and rest upon the bottom of 
the valve. Externally the shell is smooth in the umbonal regions, but anteri¬ 
orly is covered with low, rounded plications crossed by fine concentric lines. 
The systematic relations of this species are very interesting. It is associa¬ 
ted with Porambonites in the lower Silurian faunas about St. Petersburg and 
in Scandinavia, and its similarity to that genus in contour and, to a certain 
extent, in details, is apparent. 
While Porambonites is strongly orthoid in the structure of its cardinal feat¬ 
ures, and Noetlingia possesses the simple linear cardinal process of Platystro- 
PHiA, Atrypa nucella adds to these orthoid features the cardinal process of a 
streptorhynchoid, like Triplegia and Mimulus, thus presenting another point of 
tangency between these shells and the pentameroids; or, more precisely, 
another phase in the development from the comprehensive primordial stock 
represented by Protorthis, Billingsella, etc., toward the full and typical 
expression of Orthis, Orthothetes, Strophomena and Conchidium. 
