RAYMOND AND BARTON: AMERICAN SPECIES OF CERAURUS. 535 



American Museum of Natural History in New York shows that the 

 lithology is very unlike the yellow-weathering rock of the Cincinnati 

 region, and, moreover, the specimen is labeled as coming from Middle- 

 ville, New York. 



This species contains the largest specimens of Ceraurus now known. 

 The largest specimen so far seen is one in the Museum of the Geologi- 

 cal Survey of Canada. It was collected by the late H. C. Vennor at 

 Belleville, Ontario, and must have been, when complete, over 100 mm. 

 long and 85 mm. wide. It was a veritable giant, when compared with 

 the average specimen of Ceraurus pleurexanthemus from Trenton Falls, 

 and nearly double the length of the largest specimens found there. 

 The spines on the pygidia of this species grow to great length. The 

 spines on the type, which is 84 mm. long, are 27 mm. long, and we have 

 seen several which had longer ones. The spines on a pygidium col- 

 lected by the senior author near the base of the Trenton at Heeley 

 Falls, Ontario are 38 mm. long. 



Measurements. — The holotype is 83 mm. long, 60 mm. wide at 

 the genal angles, the cephalon is 24 mm. long, the glabella 17.5 mm. 

 wide at the front and 15.5 wide at the neck-ring. A somewhat smaller 

 specimen from Cobourg, Ontario, is 74 mm. long, 54 mm. wide at 

 the genal angles, the cephalon is 22.5 mm. long, the glabella is 17.5 mm. 

 wide at the front and 13.5 wide at the neck-ring. 



Formation and Locality. — This species is, so far as we now 

 know, confined to the Trenton, but it seems to be found all through 

 that formation, although especially common in the lower part. It is 

 known to occur at the following localities, and it will probably be found 

 at numerous other places, especially in the Central States : — Middle- 

 ville, New York (exact horizon not known); Roaring Run, East 

 Martinsburg, New York, (in strata corresponding to the crinoid beds 

 of the Ontario section) ; Belleville, Ontario, (crinoid beds) ; Cobourg, 

 Ontario, (sponge beds at top of Trenton); Heeley Falls, Ontario, 

 (Dalmanella beds at base of Trenton); Trenton and Peterboro, On- 

 tario, (Prasopora beds); Fenelon Falls and Kirkfield, Ontario, (crin- 

 oid beds, very common) . The type was collected at Van Kleek Hill, 

 east of Ottawa,' Ontario, by Sir William Logan, and the exact horizon 

 is not known. 



Ceraurus hudsoni Raymond. 



Ceraurus hudsoni Raymond, Annals Carnegie mus., 1904, 3, p. 367, 



pi. 14, fig. 15; 7th rept. Vermont state geol., 1911, p. 24, pi. 36, fig. 15. 



This species was described as differing from Ceraurus pleurexantke- 



