842 Report or THE StaTE GEOLOGIST. 
Lycophoria, Lahusen. 1885. 
(Plate 45, figs. 36-38.) 
Valves rotund and without median fold or sinus, so that the 
anterior margin of contact is almost straight, or very gently 
sinuous. Beaks full and closely incurved, only the pedicle-valve 
appearing 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 for- 
ward 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 anteriorly is covered with low, rounded 
plications crossed by fine concentric lines. 
Type, Zycophoria nucella, Dalman (sp.). 
Distribution. Lower Silurian. 
Conchidium, Linné. 1753. 
(Plate 46, figs. 1-14.) 
Synonyms; Gypidia, Dalman, 1828; Zdimir, Barrande, 1881; 
Antirhynchonella, Quenstedt, 1871. 
Shells elongate-subtrigonal or subpentagonal in outline, strongly 
inequivalve, biconvex; median fold and sinus faint, if at all 
developed. Anterior margins of contact usually straight, with 
sometimes a faint fold, at others a low sinus on both valves. 
Surface with numerous sharp or rounded, simple or divided 
plications extending from beaks to margins; cardinal slopes 
broad and usually smooth. 
In the pedicle-valve the umbo is elevated, attenuated, more or 
less incurved, not prone upon the opposite valve. No cardinal 
area is developed. The delthyrium is very broad and bears a 
concave deltidium, which, however, is frequently wanting. 
Teeth small, supported by convergent lamellz which unite in 
the interior cavity and form a single median vertical septum of 
variable length ; in the typical species usually extending almost, 
and sometimes quite to the anterior margin, and vertically, for 
94 
