'I'kilohitks of the Chazy LiMEsroNK. 345 



guished. The following measurements give the proportions of the 

 various i)arts. 



An entire specimen: length 57 mm.; width at the genal angles 

 31 mm. Length of cephalon 16 mm., width between eyes 16 mm. 

 Length of thora.x: 20.5 mm., width of axis 12 mm. 



An abdomen shield and part of thora.x : width of thorax at pos- 

 terior end 26 mm.; width of axis 12 mm.; length of pygidium 17 

 ram.; width 25 mm. 



Three pygidia have the following dimensions. 1. Length 26 mm., 

 width 40 mm. 2. Length 19 mm., width 28 mm. 3. Length 5.5 

 mm., width 8.5 mm. 



Locality. — The entire specimen is from Smugglers Bay, Valcour 

 Island, and the pygidium and partial thorax from the lake shore of 

 Valcour, New York. The species occurs abundantly at Crown Point, 

 Valcour Island, Plattsburgh and Chazy, New York. 



Isotelus angusticaudum sp. nov. (Plate 13, figures 3, 4.) 

 This is a form but rarely met with, although there are several speci- 

 mens in this collection and also a number in the collections of the 

 United States National Museum. Only pygidia have been found, but 

 they are very different from the pygidia of any of the other species 

 which occur in the Chazy. 



Description. 



Cephalon and thorax unknown. 



Pygidium narrow, strongly and uniformly convex, tapering rapidly. 

 Sides nearly straight, the margin slightly concave and very steep, axis 

 not strongly marked, wide and low. There are no traces of annula- 

 tions on the axis nor of ribs on the pleura. 



One specimen is 18 mm. long and 19 mm. wide ; a second 27 mm. 

 long and 27 mm. wide ; a third, 35 mm. long and 36 mm. wide. 



Locality. — The type specimen is in the writer's collection and is 

 from the north end of Valcour Island. The species is also found on 

 the east side of Valcour Island, at Chazy, and Isle La Motte, Vt. 



Isotelus? bearsi sp. nov. (Plate 10, figures 21-25.) 



Along w'ith Asaphtts i/itirgi/ialis occurs another Asaphiis of a type not 



common in America. This is a species with protruding eyes, much 



resembling the Asaphus Kowalcivskii oi \\\<t Lower Silurian of Russia, 



but not of so extreme a type. As usual the material consists of cranidia, 



