198 



This may be only a variety of D. Oweni ; but owing to the greater 

 proportional width and smoothness of the glabella, and the absence of a 

 marginal rim to the head, it has a different aspect. 



Locality and Formation. Point Le*vis ; in limestone No. 2, Quebec 

 group. 



Collector. T. Devine, Esq. 



DlKELOCEPHALUS SE30STRIS. (N. Sp.) 

 Fig 184. 



Description. Glabella oblong, sub-cylindrical ; most convex along the 

 median line ; front abruptly but not strongly elevated ; outline, on a side 

 view, nearly straight for two-thirds the length, then rather suddenly curved 

 down to the front ; sides a little concave about the mid-length, nearly 

 straight and parallel ; anterior angles rounded ; front margin gently con- 

 vex: or straight in the middle. Neck furrow extending all across and 

 turned forwards at the extremities, not quite reaching the dorsal furrows ; 

 posterior furrows, with their anterior extremities, a little behind the 

 middle, extending across with a strong backward curve ; anterior furrows, 

 with their anterior extremities, just behind a line drawn across at the 

 anterior third, then curving backwards, sometimes absent or only impressed 

 near the sides. In general all the furrows terminate without reaching the 

 sides of the glabella. The dorsal furrow is distinctly impressed, but very 

 narrow. The eyes are small, their centres situated j.ust in front of the 

 mid-length, and almost in contact with the side of the glabella. The 

 anterior margin of the head is narrow, thin, and turned upwards, as it is 

 in D. Rising erL 



Length of glabella 5 lines ; width 4 lines ; width of the front margin 

 of the head J a line. 



This species, together with the two that I have placed in the genus 

 Arionellus, under the names A. cylmdricus and A. subclavatus,* will 

 certainly fall into the newly proposed genus Ptychaspis J if that generic 

 name be sustained. Ptychaspis seems to me to differ scarcely at all from 

 Bathynotus. J A species, almost identical with D. Sesostris, occurs in 

 the upper part of the Potsdam at Whitehall, New York. 



Locality and Formation. Point Ldvis ; in limestone, No. 1, Quebec 

 group. 



Collectors. T. Devine Esq., T. C. Weston. 



* Geology of Canada, p. 237. 



f Ptychaspis (Hall). 16th Rep. Reg, N. Y., p. 170, 1863. A genus proposed to 

 include species of the type of D. Miniscaensis (Owen). Potsdam sandstone. 

 Bathynotus (Hall). 13th Rep. Reg. N. Y., p. 117, 1861. 



