46 Bulletin 6 46 



B. Body not very oblique. 



B. Surface marked by concentric striae which curve backward 

 between the radii. 

 fii. Strong radii, usually without interstitial additions. 



A. boydi. 

 (i2. Slender radii with interstitial additions. 



bi. Body broadly ovate; oblique, at an angle of about 55°. 



A. theta. 

 b2. Body broad and short ovate; oblique, at an angle of 

 about 45°. A. eta. 



B' . Surface not marked by concentric striae which curve back- 

 ward between the radii. 

 ji' I. Strong elevated rays and wider interspaces. 



A. epsilon. 

 ft'2. Radii, fine. 



b'l. Body at an angle of about 60° with the hinge. 



A. delta. 

 b'2. Body at an angle of about 45° with the hinge. 

 b'l. Shell small, body subrhomboidal, subovate. 



A . perstrialis. 

 b'2. Shell of medium size, rhomboidal, body broadly 

 ovate, A. iota. 



C. Body very oblique. 



Radii filiform, interrupted and undulating. A. kappa. 



Crustacea. 



Phacops ra7ia Hall. 



This species is abundant at a single localitj' in the Ithaca 

 group, station 8-4. 



Mesothyra oceani Hall. 



This is a rare species in the Portage group. 



Vertebrata. 



Pisces. 



Dipterus ithacensis H. S. W. 



Lower Ithaca group and Ithaca shale. — H. S. Williams. 



