'rklLOlIITES OK THE ChAZY Li.MESTONE. 373 



DeSCKII'IIOX. 



Glabella almost globular, length and breadth about ecjual. There 

 are three pairs of glabellar furrows : the first two pairs faint or not 

 visible at all ; the posterior pair deep, curving round to meet the neck 

 furrow, isolating the posterior glabellar lobes. Neck segment narrow 

 and the furrow deeply impressed. Fixed cheeks small, rounded at the 

 genal angles, and with a wide border all around. Eye evidently 

 large, opposite the next to the last pair of glabellar lobes and close to 

 the furrow which outlines the glabella. There is a narrow rim anterior 

 to the glabella. The whole surface is finely tuberculated. 



Measiirenicnts. — Cephalon : length 3. 5 mm.; width 6 mm.; width 

 of glabella, 3.5 mm. Another cephalon : length 3 mm.; width 4 

 mm.; width of glabella, 2.75 mm. A glabella : length 8.5 mm.; 

 width S mm. 



Locality. — Common all through the Chazy limestone at Chazy, 

 Valcour Island, Valcour, New York and Isle La Motte, Vermont. 



Rkmarks on the oenus Cheirurus. 



In reviewing the species which Ijillings has placed under the genus 

 Cheirurus, it seems that the group is capable of some subdivision. For 

 the American species, Clarke, in the Paleontology of Minnesota, has 

 outlined a classification by which all are placed as species of Ccraurus 

 and its subgenera Cyrtonetopus, Fseudosphccrexoc/ws, NieszkoiC'skia, 

 Spiurrocoi-phe, Eccoptochile and Crotalocephalus. While his arrange- 

 ment produces some natural groups, yet, as it is constructed on an arti- 

 ficial basis, it produces confusion in other groups. Only that part of 

 the scheme which affects the Chazy species is here taken up. 



Of the genus Ceraurus (sensu stricto) there are in the Chazy two 

 species, Ceraurus hudsoni and Ceraurus pompilius, which evidently ful- 

 fill all the requirements of the genus by agreeing with the type spe- 

 cies, Ceraurus pleurexairtheiniis Green. In the subgenus Cyrtometopus, 

 the species C. opollo Billings, C. mercurius Billings, and C. scofieldi 

 Clarke were associated. Cyrtovietopus scofieldi Clarke differs from 

 CV/-rt;//r«i- (restricted) only in the faintness of the first two pairs of 

 glabellar furrows, and, in general, is very similar to Ceraurus poiupilius 

 Billings, in which species the anterior furrows are sometimes rather 

 poorly impressed as compared with those of Ceraurus pleurexanthemus. 



Cheirurus opollo Billings strongly resembles Cheirurus vulcanus, 

 although the eyes are further forward, and it is probably nearly related 



