'I'kii.onriK.s ok thi'. C'hazv Limes ione. XV.) 



Ainpyx Ilalli Billing-^, iS6r, (ieological Survey of Vermont, volume II, page 959) 



figure 365. 

 Anihyx halli \'o(lges, 1S93, American Geologist, volume XI, page 106, figure 5. 



One of the common trilobites of the Chazy limestone is the little 

 Amp>yx which Billings describeil from Highgate Springs, Vermont. 

 In spite of the frequency with which it is met, no complete speci- 

 mens have yet been found. Pygidia, although small, are frequently 

 obtained, but of the thorax only the last two segments have been 

 foimd. 



An examination of the type specimen at Ottawa shows that the ])ygid- 

 lum of that specimen has attached to it the last two thoracic seg- 

 ments, which explains the surprising length of the pygidium figured 

 in the Paleozoic Fossils of Canada, page 24. A similar specimen was 

 found by the writer on \'alcour Island. 



Description. 



Cefyhalon. — C'ranidiuni triangular, the greatest width at the neck 

 segment. The glabella e.xtends about half its own length beyond the 

 anterior angles of the fixed cheeks, and is then prolonged into along, 

 fluted spine, which curves gently upward. This spine is prismatic, 

 with a deep furrow on each of its four sides. The furrow on the upper 

 side extends back to about the region of the fixed cheeks. Glabella 

 widest at the anterior angles of the fixed cheeks and contracting pos- 

 teriorly, so that it forms about one fifth of the whole width at the 

 neck segment. On the cast there are two small nodes on each side of 

 the glabella near its posterior end, one pair a little in front of the other. 

 A distinct carina extends along the top of the glabella to the posterior 

 end of the dorsal furrow on the rostrum. 



Thorax. — A specimen from Valcour Island retains the last two 

 segments of the thorax. They are narrow, extend horizontally, and 

 on the pleura are deeply grooved. The fourth segment is 5 mm. 

 wide, .3 mm. long, and the axis is 1.6 mm. wide. The pygidium of 

 the same specimen is 1.25 mni. long, 4.3 mm. wide, and the axis is 

 1.3 mm. wide at the anterior end. 



Pvgiditun. — The pygidium is about three times as wide as long, 



' usually regularly rounded posteriorly, sometimes somewhat triangular. 



Axis wide, prominent, extending to the posterior end of the pygidium. 



The exfoliated axis shows seven to ten pairs of nodes very similar to 



those noticed by Ruederman on specimens of LoncJiodonius liastaiiis 



