468 DR F. A. BATHER. 



§ 432. Pleurocystis anticostensis. 



1857. Pleurocystites anticostensis E. Billings, Geol. Surv. Canada, Rep. Progr., 1856, p. 288. 



1858. Pleurocystites anticostiensis Bill., E. Billings, Canad. Org. Rem., dec. 3, p. 52, pi. 1, f. 3. 

 1866. Pleurocystites anticostiensis Bill., E. Billings, " Catal. Silur. foss. Anticosti," p. 8. 

 1899. Pleurocystites squnmosus, var. a7iticostiensis Bill., O. Jabkel, " Stammesgesch. d. Pelmat.," 



p. 234. 



§ 433. Diagnosis. — A Pleurocystis [with sides of theca unknown] ; shoulder-angle 

 apparently ca. 65° ; ratio, width : height, of plate 5, circa '97. Pectinirhombs all 

 present, with slight rounded border, all elongate, lanceolate; in 10-14, sutural axis: 

 transverse axis : : 5 : 2 (approximately) ; folds in all uncovered. [Anal face unknown.] 

 Ornament of antanal face slight concentric folds, smooth. Columnals with coarse 

 vertical ridges on flanges which appear nodulose. 



§ 434. Locality.— Charleton Point, Anticosti Island. 



§ 435. Horizon. — Hudson River Group. 



§ 436. Type-material. — The single imperfect specimen figured by E. Billings 

 (1858) is the holotype. No others have been recorded. 



§ 437. Remarks. — P. anticostensis is reduced to a variety of P. squamosa by 

 Jaekel (1899); but there are definite points of difference known, and others may be 

 expected in accordance with the undoubtedly later age of the species. 



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



§ 438. Pleurocystis mercerensis. 



1895. Pleurocystites mercerensis S. A. Miller & W. F. E. Gurley, Bull. Illinois State Mus., 



No. 6, p. 60, pi. 5, ff. 25, 26. 

 1899. Pleurocystites mercerensis Miller & Gurley, 0. Jaekbl, "Stammesgesch. d. Pelmat.," 



p. 234. 



§ 439. Diagnosis. — A Pleurocystis with sides of theca convexly curved forming a sub- 

 ovate outline ; shoulder-angle ca. 75° ; ratio, width : height, of theca, circa '95 ; of plate 

 5, ri ; plate 3 descends below stem-attachment [amount unknown]. Pectinirhombs all 

 present, with well-marked border, all widened, elliptical [ratio unknown], folds in all 

 uncovered. [Upper part of anal face unknown.] Periproctals " very numerous minute." 

 Ornament of antanal face said to be radiate. [Columnals unknown.] 



§ 440. Locality. — Mercer co., Kentucky, U.S.A. 



§ 441. Horizon. — Trenton Group. 



§ 442. Type-material. — The unique specimen in the Gurley collection, presumably 

 now at Chicago University, is the holotype. 



§ 443. Remarks. — The description by Miller & Gurley unfortunately pays 

 more attention to features common to the whole genus, than to such as might have 

 proved characteristic of the species. Moreover, the statement that "the plates 

 are radiately sculptured," though confirmed by the figure, must be viewed Avith caution ; 

 and the fact that " the column is elliptical" may indicate merely that the specimen is 

 slightly crushed. 



