307 



posed, and the siphuncle is ventral and marginal. It is difficult to see 

 how two of the large specimens figured by Hall as Lituites undatus, or the 

 small specimen from Poland that Hyatt figures as Eurystomites undatus, 

 can be distinguished generically from Plectoceras. 



All the specimens from the Province of Quebec that were formerly 

 identified with Lituites undatus are Plectoceras Halli. The only specimen 

 that the writer has seen, that was certainly collected in Canada and that 

 is probably referable to Plectoceras undatum (ov, as Hyatt calls it, to 

 Eurystomites undatus) is the original of the figure on Plate 37. It was 

 obtained, a few. years ago, from the Black River limestone exposed in an 

 excavation for a sewer in a street not far from Queen's College, Kingston, 

 and has recently been acquired for the Museum of this Survey, in ex- 

 change, from the authorities of Queen's University. It is a cast of the 

 interior of the septate portion of the shell, five inches and a half in its 

 maximum diameter, with fragments of the test attached. Its outer volu- 

 tion is subquadrate in transverse section, and the sutural lines are nearly 

 straight on the sides, but shallowly concave on the venter or periphery. 

 In the Museum of Queen's University there are two large specimens of 

 P. undatum ('or Eurystomites undatus) that are supposed to have been 

 collected from the Black River limestone at or near Kingston, but it is 

 not at all certain where either of them are from. 



If a Plectoceras, P. undatum is obviously a much larger species than P. 

 Jason or P. Halli. 



Eurystomites plicatus, nobis, from the Galena-Trenton formation of 

 Little Black Island, Lake Winnipeg, which is described and figured in 

 the third part of this volume, has much the appearance of a Plectoceras, 

 externally, but its siphuncle is known to be "ventrad of the centre." 



The genns Barrandeoceras also was first described by Hyatt in 1883, in 

 his " Genera of Fossil Cephalopoda," already referred to as having been 

 published in the twenty-second volume of the Proceedings of the Boston 

 IvTatural History Society. On page 299 of that memoir it is placed in 

 the family Nautilidse, and is thus described : 



" Barrandeoceras, nobis, includes gyroceran and nautilian shells with 

 very large umbilical perforations, and compressed, slightly costated or 

 smooth whorls, generally without an impressed zone, though this is some- 

 times present. The venter is narrower than the dorsum, the siphon near 

 but above the centre, septa deeply concave, and sutures with ventral sad- 

 dles, lateral lobes and dorsal saddles, without annular lobes. Type, Barr. 

 (Naut.) natator, sp. Bill. Can. Nat. N.S., vol. 4, Mus. Geol. Surv. Can. 

 The genus also includes the Bohemian forms Barr. (Naut.) Bohemicum, 

 sp. Barr., Vol. 2, Syst. Sil. pi. 32, S3 ; Sternbergi, ibid., pi. 36, 37 ; 

 5 



