34fi AxxALs OF- THE Carnk(;iic Museum. 



free cheeks, and pygidia, specimens of all of which are quite abundant 

 at the Sloop Bay locality on \'alcour Island. 



Description. 



Cephalon broad, smooth, flattened on top, with abruptly rounded 

 slopes. Cranidium smooth, flattened, marked by two deej) dorsal 

 furrows as in lUirmis. These furrows start back of the eves, run 

 inward, and around close to the base of the eye stalks, then outward 

 again to the margin. Indistinct glabellar furrows can sometimes be 

 seen, and on casts of young individuals are four pairs of faint depressions. 



Eyes large, raised high above the surface of the head on stalks. 

 Free cheeks relatively small, nearly reaching each other around the 

 front of the head by long'spiniform projections. Genal angles rounded. 

 Around the margin of the free cheeks is an extremely narrow striate 

 border. 



Thorax unknown. 



Pygidium almost semicircular, very evenly convex, with the axis 

 only faintly indicated. There are slight traces of ribs on the pleura 

 and a flattened border extends all around. This pygidium somewhat 

 resembles that of Isoteliis obtusus Hall, but it may be distinguished 

 from that species by the absence of punctse, the presence of a depressed 

 border, and by the entire frontal margin. 



Measurements. — A cranidium: length 15 mm.; width between 

 tips of free cheeks 22 mm.; between bases of eyes 8.5 mm. Another 

 cranidium is 21 mm. long. The eyes stand 5 mm. above the surface 

 of the cranidium or a total height of 12 mm. above the lateral mar- 

 gin of the cephalon. One pygidium is 11 mm. long and 16 mm. 

 wide, while another is 21 x 27 mm. 



This species is closely allied to Asaphus scuta/is from Caradoc, 

 which Salter referred with some doubt to the section Cryptomnws 

 Eichwald. Both cephalon and pygidium of our species diffef from 

 Asaphus expatisus, the type of Cryptonymus, but the cephalon also dif- 

 fers much from the typical Isotelus in its stalked eyes, deflected front 

 and deep dorsal furrows. The cranidium considerably resembles that 

 of the genus Illcenurus, but the eyes are much more elevated, the free 

 cheeks narrower, and the anterior ends of the facial sutures much 

 nearer together. 



Locality. — Found only in the trilobite layers in Sloop Bay, Valcour 

 Island, New York, in the middle of the Chazy. 



