482 DR F. A. BATHER. 



resembling the latter in the absence of pectinirhomb 1-5, and in the general character 

 of its ornament. The small number of folds in pectinirhomb 10-14 is another point 

 of likeness. It resembles P. Rugeri, but differs from P. anglica, in the hexagonal 

 shape of plate 5 and in the absence of any plate between 2 and 6. From both these 

 species, moreover, and especially from P. Pugef^i, it differs in the greater relative 

 height of both theca and plate 5. Indeed, in its proportions, it stands in marked 

 contrast to those species, and differs in the same way, if to a less extent, from all 

 other species mentioned in this memoir. This fact is marked by the name procera. 



Pleurocystis quadrata n. sp. 

 (PI. VI. figs. 69-74. Text-figs. 73, 79.) 



§ 501. Diagnosis. — A Pleurocystis with markedly subquadrate theca ; shoulder- 

 angle 100° (to 115°); ratio, width : height, of theca, "9 (to I'Oo); of plate 5, 

 1'09; plate 3 descends to about third flange. Pectinirhombs all present, with 

 variable border; all widened and rhomboid or trapezoid; in 10-14 are 25 to 

 28 folds, sutural axis : transverse axis : : 100 : 125 ; folds on 14 and 12 partly 

 covered. Plate 12 separated from 14 by the whole width of 18. Maximum diameter 

 of periproctals 1*4 mm. in larger individuals (to "9 mm. in smaller individuals). Orna- 

 ment of antanal face, strong radiate ridges, a few strong rhomb-ridges, traces of 

 concentric granulation. Stem proximally with bold flanges bearing granules in 

 vertical series. 



§ 502. Locality. — Thraive Glen, Girvan. 



§ 503. Horizon. — The Starfish Bed in the Drummuck Group (§ 6). 



§504. Material.— G 171, holotype (PI. VI. figs. 69-71), and G142, paratype 

 (PI. VI. fig. 73). Associated more doubtfully are Gl74, Gl75 (PL VI. fig. 74), 

 G190, and Gl92. 



§ 505. Description of Specimens. — ^This follows the holotype, and is confirmed by 

 G142, except where otherwise stated. 



The sides are parallel up to the level of the pectinirhombs, and are almost at right 

 angles to the basal line of the theca, thus producing a markedly subquadrate outline, 

 the effect of which is increased by the exceptionally wide shoulder-angle, 100°. Hence 

 the trivial name quadrata. 



Thecal height, 28*2 mm.; width, 25*5 mm. 



§ 506. Plate 5, height, 9 "6 mm.; width, 10*5 mm. 



§ 507. Plate 3 descends to between the second and third flange, and the lobation on 

 the other side of the stem reaches to about the top of the second flange. 



§ 508. The Pectinirhombs are all well developed, and all widened across the 

 suture, but not excessively. 



Pectinirhomb 1-5 is almost lozenge-shaped, with a thick raised rim and 15 un- 

 covered folds; sutural axis, 3*2 mm.; transverse axis, 5 7 mm. 



