464 DR F. A. BATHER. 



§ 403. Pleurocystis squamosa. 

 (Text-figs. 63-65.) 



1854. Pleurocystites squamosus E. Billings, Canad. Journ., vol, 2, p. 251, fF. 9-12. 



1857. Pleurocysiites squamosus 'B\\\., E. Billings, Geol. Surv. Canada, Rep. Progr., 1856, p. 286. 



1858. Pleurocystites squamosus Bill., E. Billings, Canad. Org. Rem., dec. 3, p. 49, pi. 1, ff. la-d. 

 1896. Pleurocystis squamosa Bill., E. Haeckel, "Amph. und Cyst.," Festschr. Gegenbaur, 



vol. 1, pp. 37, 44. 

 1899. Pleurocystites squamosus Bill., O. Jaekbl, " Stammesgesch. d. Pelmat.," p. 234 (pars). 



§ 404. Diagnosis. — A Pleurocystis with thecal sides nearly parallel up to the level 

 of rhombs 11-12, 10-14, giving a subquadrate outline; shoulder-angle ca. 75°; ratio,, 

 width : height, of theca, '8 ; of plate 5, '9 ; plate 3 descends to below third flange. 

 Pectinirhombs all present, flat or slightly concave, with raised border ; all widened ; 

 10-14 and 11-12 lozenge-shaped, 1-5 elliptical; in 10-14 sutural axis : transverse 

 axis :: 2:3, in 11-12 :: 3 :4; folds in all uncovered. Plates 12 and 14 just meet 

 below 18. Periproctals average 1 mm. in diameter, range from 1"25 mm. near centre 

 to '5 mm. at margins. Ornament of antanal face obscure, rhombic, and concentric. 

 Column als vertically ridged on flanges and swellings. 



§ 405. Locality. — Ottawa, E. Billings. Recorded from Pakenham, Ont., H. M. Ami 

 (Jan, 1905, p. 84 J) ; and near Kirkfield, Ont, F. Springer (1911, p. 45). Also at 

 Hull, P.Q., colln. W. R. Billings and Brit. Mus. B16036 ; and at Belleville, Ont., 

 Brit. Mus. E15923, E15925 (text-fig. 65), E16045 (text-figs. 63, 64), E16048, 

 E 16049, all colld. W. R. Smith. 



§406. Horizon. — "Trenton Limestone near the middle of the formation," 

 E. Billings ; and in the lower part, Springer. The precise meaning of this may be 

 gleaned from Raymond (1912, p. 354). Mr Raymond divides the Trenton Limestone 

 of the Ottawa valley into six horizons, each containing a bed of limestone. The 

 lower beds 1 to 4, with a combined thickness of 165 feet, are distinguished as the 

 Kirkfield Limestone series. Of these Horizon 2, a thick- and thin-bedded blue lime- 

 stone, with chert in flat plates parallel to the bedding, occurs at Kirkfield lift-lock and 

 at the Hull quarries ; it contains Pleurocystis and other Pelmatozoa. Horizon 5, next 

 above the Kirkfield series, is a thin-bedded light grey limestone, with thin shale 

 partings ; it contains Pleurocystis and Pelmatozoa similar to those of Horizon 2. Since 

 the combined thickness of Horizons 5 and 6 is 150 feet, and since the lowest Horizon 



of the Kirkfield series is poorly exposed near Ottawa, it may be inferred that E. Billings 



alluded to Horizon 5. 



§ 407. Type-material. — In the original description only two specimens were 



definitely mentioned, and both were figured. These, then, are syntypes. I hereby 



select as holotype the original of Billings' figure 9. 



The ratios have been based on Billings' description and his pi. 1, £ la (1858); his 



account has been checked by the British Museum specimens mentioned above (§ 405). 

 Comparison with other Species. — See §§ 551-553. 



