Raymond : Notes on Ordovician Trilohites. 77 



Subgenus IIkliomeka Riunioiul. 

 Heliomera sol (Billings). 



Plate XVIII. figure 12. 

 Cheirurus sol Billings, Paleozoic Fossils of Canada, I, 1865, 288, fig. 276. 

 Heliomera sol R.wmond, American Journal of Science, series 4, XX, 1905, 381. 



Description. 



Cephalon short, wide, the glabella very large and flattened, the cheeks 



small. Glabella almost semicircular, with three pairs of long narrow 



glabellar furrows, all of which turn backward on their inner ends, each 



joining the one back of it, and the third pair joining the neck-furrow, thus 



Fig. 9. Heliomera sol (Billings). Glabella and fragments of frontal border^ 

 X 4- 



producing a central lobe like that of AmphiUchas. This central lobe is 

 of uniform width up to the inner ends of the first pair of glabellar furrows, 

 but expands suddenly in front of them. Toward the front of the median 

 lobe there is a slight depression, suggesting the median furrow in Pliomera. 

 The first pair of glabellar furrows run backward at an angle of about 45°. 

 the second pair at a smaller angle, while the third pair are nearly parallel 

 to the neck-furrow. The glabellar lobes are narrow and club-shaped. 

 The neck-ring is wide, flat, and separated from the glabella by a deep 

 furrow which extends the whole width of the cephalon. The cheeks are 

 not sufficiently well preserved to be described, but enough of the test 

 remains to show that the outline of the cephalon was similar to that of 

 Pseudosphcerexochus vulcanus. There is a narrow smooth border all 

 around the front, and the surface of the glabella is covered with fine 

 tubercles. 



The relations of this species are rather doubtful. From the form of the 

 cephalon it seems to belong close to PscudosphcBrexochiis, but there has 

 not been seen in any of the species of that subgenus a tendency to vary 

 in the direction of an isolated central lobe and long isolated glabellar lobes. 

 The glabellar furrows in the various species are usually faint, never deeply 



