'rkll.oKI IKS ol I'HE C"HA/V LiMKsrONE. 3f)9 



tively large. I'lyes small, very close to the glabella, and o])posite the 

 ends of the i)osterior jiair of glabellar furrows. Entire cephalon 

 bounded by a rather wide convex border. Surface sparsely covered 

 with small tubercles. 



Measurements. — Length of cephalon 13 mm.; width 26 mm. Width 

 of glabella behind 13.5 mm. Width of glabella at the first pair of fur- 

 rows 8 mm. Width between eyes 13.5mm. 



Locality. — The specimen figured — the only one the writer has 

 seen — was collected by Mrs. Eleanor M. Hudson, who has very 

 kindly allowed me to use the specimen for description. Acidasi)is 

 layers. Smuggler's Ray, Valcour Island. 



Pseudosphaerexochus vulcanus variety billing.'^i, variety nov. (Plate 14, figure 



'7.) 

 Cheiriirus I'ulcanits Billings, 1S65, Paleozoic Fossils Canada, volume i, page 324, 



figure jlOc?, /', ( . 

 Not Cheinnns 'rultanus liillings, 1865, Paleozoic Fossils Canada, volume 1, page 



284, figures 2~\a, h, c. 



At Standbridge, where Clieintrus vukaniis has been found in the 

 Quebec group, it is accompanied by a variety which Billings figures 

 in the paper cited above. This variety differs from the form just de- 

 scribed, in having a narrower and much more elevated glabella, which 

 does not taper so rapidly in front, while the posterior part of the gla- 

 bella, instead of sloping down to the neck ring, is very high and 

 abrupt, sometimes almost spiniform. (See figure 11.) 



This variety occurs also at Valcour Island, where two specimens 

 have been found by I'rofes.sor Hudson in the Trilobite layers at Sloop 

 Bay. The whole aspect of the cephalon is so different from the typi- 

 cal form of the species that it will be found convenient to distinguish 

 it by the varietal name, /'////// 1,'-^-/. 



Pseudosphaerexochus approximus sp. nov. (Plate 14, figure 18.) 



Cf. Clu'iruriis prolificus Hillings, Paleozoic Fossils, Canada, volume I, plate 2S5, 

 figure 273. 



In the collection from the trilobite layer on the east side of Valcour 

 Island is the glabella and fixed cheek of a species of C/ieiriiri/s which 

 was at first identified with C/ieinin/s prolificiis, but which a closer 

 examination shows to differ somewhat from that form, though they 

 must be closely related. Clieintrus vulcanus Billings, with which C. 

 prolificus is probably identical, is also very similar. 



