266 ROYAL SOCIETY OF CANADA 
species that made them are not known. The large forms of Eophyton 
(EB. Jukesi ?), those having bands of long, straight or arched and parellel 
striæ, which the writer has referred to Ctenichnites, have been found at 
several horizons ranging from the lowest Cambrian to the Silurian (Upper) 
and so give but little help. The remains of animals actually found, -Lin- 
gulidæ and Trimerellidæ, appear to have their best known analogues in 
the Silurian (Upper) and are at least as late as the Ordovician age. 
ORTHIDUE. 
CLITAMBONITES, Pander. 
CLITAMBONITES (GONAMBONITES) PLANA, Pander, var., PI. IT, Figs. la 
to le. 
Gonambonites plana, Pander, Beitr. zur geogn. Russl. p.78, pl. 16. 
Orthis plana, deVerneuil, Russ. and Ural M’t’ns, vol. ii., p. 199, pl. xi., fig. 7a-h. 
Clitambonites plana, Hall and Clarke, Gen. Palæoz. Brachiop. pl. vii., fig. 28. 
The following is de Verneuil’s description of this species: “ Shell 
semi-elliptical, depressed, with sharp edges, horizontal, not sinuous, and 
having its greatest width at the cardinal border. Ventral [dorsal] valve 
but little convex, provided with a very feebly marked sinus, and an area 
inclined almost 60° on the plane of the lateral edges. This area is two or 
three times less elevated than the area of the dorsal [ventral] valve, has 
in the middle a triangular slit, closed by a convex deltidium, which meets 
the deltidium of the opposite valve, and intercepts all apparent com- 
munication from the interior to the exterior. Under the deltidium in the 
form of a lip is found as in the preceding species [ Orthis inflexa] a median 
tooth and two small lateral teeth. The dorsal [ventral] valve is flat and 
having depth only toward the area ; this, high and a little recurved, is 
inclined like the area of the opposite valve, about 60° from the plane of 
the lateral edges.; its surface is smooth and shows no vertical striæ. The 
triangular slit is narrow, and its angle at the summit from 30° to 40°. 
The surface of the two valves is covered with rAdiating striæ, fine, equal, 
several times dichotomous in their length, and not increasing in their 
size from the beak to the borders : at 10 millimetres from the beak one 
may count about 12 in the the space of 5 mm; they appear a little 
crenulated, and are interrupted by three or four transverse rings raised 
in steps. 
“In the interior one observes under the beak of the dorsal [ventral ] 
valve a kind of shield, the walls of which rise to the cardinal border, and 
abut against the two sides of triangular slit. This shield is termin- 
ated in front by a median point in the form of a beak, such as one 
ordinarily sees in many of the Cranias. The bottom of the valve is cut 
in straps, irregular and separated by a very prominent interior border 
from the edge, which is narrow and striated.” 
