209 



This is the first example known to me of the occurrence 

 of Cranle in the Silurian rocks of this country. 



Crania setifera (Hall). 



Shell circular, depressed convex, apex central or slightly 

 excentric, small, pointed or mammiliform. Surface of up- 

 per valve closely covered with minute setiform spines, di- 

 rected from the apex towards the margin. Lower valve 

 unknown. 



When the setae are removed, the surface appears strongly 

 punctate, a character which distinguishes this from C. silu- 

 riana. 



GENUS PHOLIDOPS (Hall). 



Pholidops ovalis (Hall). 



Shell round oval, somewhat broader anterior to the mid- 

 dle ; valves equally convex ; apex situated about one-third 

 the length of the shell from the posterior end. Surface 

 marked by concentric lines of growth which are strongly 

 lamellose towards the margin. 



This species differs from P. (Orbicula) squamiformis of the 

 Niagara group of New York, in the greater convexity, more 

 closely arranged concentric lines of growth, and in being 

 more regularly and broadly oval. 



GENUS ORTHIS (Dalman). 



Orthis hybrida? 



A species of Orthis resembling 0. hybrida is common in 

 the locality. Two varieties of form occur ; one of them 

 narrow and ventricose, with the anterior margins thickened 

 and strongly lamellose; another rather constant variety, 

 broader and less ventricose, with sometimes a slight sinu- 

 osity in front. None of the specimens among more than 

 sixty individuals have the broad sinuosity of the ventral 



