130 The Ottawa Naturalist. [Nov. 



dium i.<^ 18 mm. long and 30 mm. wide, while another is 12 mm. 

 long and 21 mm. wide. A very large cephalon is 27 mm. long 

 and 58 mm. wide. 



This species is closely related to Baihyurus exians (Hall), 

 but differs from that species in being wider, in having a much 

 less convex axial lobe, a depressed and rotmded, instead of a very 

 convex and subtriangular pygidium, and a much wider concave 

 border on the pygidium. The surface of the glabella of B. extans 

 is quite granulose, while the test in this species is smooth. The 

 species a:lso attains a much larger size than B. extans or any other 

 species of the genus. 



Locality. This species seems to be rather common in a 

 layer of dark gray dolomitic limestone southwest of the outcrop 

 of the Black River and Lowville at La Petite Chaudi^re, 

 Mechanicsville, Ontario, and has not yet been observed in any 

 ether, stratum. This layer is supposed to belong to the Chazy. 

 ', \ The.entire specimen, which is probably the largest Bathyiirus 

 ikinoy^'n,. was collected by Mr. J. E. Narraway, and is in his col- 

 lection.. . The other specimens figured were collected by the 

 writer and are in the collection of the Geological Survey. Mr. 

 Narraway has a pygidium of this species which he collected some 

 years agOjfrom a loose fragment of rock in Ottawa South. 

 ; . The only other Bathyums known from the Chazy is B. 

 angdini Billings, a species which is peculiar in that the axial 

 lobe of the pygidium extends across the border to the posterior 

 margin., 



ISOTELUS ARENICOLA Sp. NoV. 



For a number of years fragments of a large Isotelus have 

 .been. found in the sandstone of the Chazy about Ottawa, but 

 as the cephalon was unknow^n, it was not possible to determine 

 what species was represented. It has usually been listed as 

 Asaphus or Isotelus canalis. (See Sowter, T. W. E., Ottawa 

 Naturalist, Vol. IL, pp. 11-15, 1888; Ami, H. M., Appendix to 

 Dr. Ells' "Geology of Ottawa and Vicinity," 1901). A free 

 cheek recently found by the writer at Britannia supplies the 

 missing information, and this, with the large headless specimen 

 collected by Richardson at Deschenes, furnishes the material for 

 the description which follows. 



Description. Cephalon, judging from the free cheek, 

 nearly, three-fourths as long as broad, surrounded by a wide 

 concave border. Eyes large, situated less than their own length 

 from' the posterior margin of the cephalon. Free cheek broad, 

 with the genal angle drawn out into a short, broad, flat spine. 

 Thorax of eight segments, the axial lobe narrow for the genus 

 one-third the total width. Pygidium roughly triangular in out- 



