barton: a new genus of the cheiruridae. 553 



three eighths of the distance across the glabella. The posterior pair 

 of glabellar furrows are straight, deep, and moderately broad, they 

 slope gently backward, and are about one third the width of the 

 glabella in length. At their inner ends a curving constriction connects 

 them with the neck-furrow. The neck-furrow is well marked, in its 

 middle-third of the axial portion parallel to the posterior margin of 

 the neck -segment, in the two outer thirds sloping backward. The 

 glabella is smooth. The fixed cheeks are of medium size and are 

 faintly pitted. The genal angles are produced into short spines. The 

 palpebral lobe is situated opposite the second and third glabellar fur- 

 rows. It is triangular, with a thickened edge, and with a deep rounded 

 furrow on the upper surface of the lobe. From the palpebral lobe a 

 faint eye-line runs to the base of the anterior pair of glabellar furrows. 



The hypostoma is, in general form, similar to that of Cheirurus in- 

 signis Beyrich, but at its posterior end, is slightly more rounded, and 

 its lateral depressions do not run quite so far back before bending in. 

 It is distinguished from the hypostoma of Ceraurus by the fact that 

 in the latter, the lateral depressions do not turn in, by a much more 

 rounded posterior point than the latter, and the more rounded termi- 

 nation to the border. 



Ceraurinus trentonensis differs slightly from other members of the 

 genus. The forward expansion of the glabella distinguishes it from 

 all the other species except Cheirurus ornatus Dalman, but in this latter 

 species the expansion of the glabella is very slight. The two pairs 

 of curving anterior glabellar furrows are also not characteristic of most 

 of the species of this genus. The smoothness of the glabella and the 

 large size of the glabellar lobes are, however, incompatible with the 

 reference of this species to Ceraurus, and the course of the 

 pair of posterior glabellar furrows excludes it from Cheirurus. As 

 its characteristics are most nearly those of Ceraurinus, it is referred 

 to that genus. The affinities of Ceraurinus trentonensis are most 

 closely with a Russian species, an unidentified specimen of which is 

 in the U. S. National Museum. From Schmidt's description of Chei- 

 rurus ingricus Schmidt l and of Cheirurus ornatus Dalman, 2 this speci- 

 men would seem to be closely allied to these species, but not to be 

 identified with either. The affinities of Ceraurinus trentonensis may 

 therefore also lie with these two Russian species. 



Formation and Locality. — Curdsville bed, at the base of the 

 Trenton, Goat Island, Manitoulin Islands, Lake Huron. The figured 



1 Mem. Acad. imp. sci. St. Petersburg, 1881, ser. 7, 30, no. 1, p. 135, pi. 6, fig. 1-2. 



2 Schmidt, hoc. cit., p. 133, pi. 6, fig. 3-4, pi. 16, fig. 1. 



