CARADOCIAN CYSTIDEA FROM GIRVAN. 479 



In the proximal region the columnals have a greatest diameter, on the flange, of 

 4 mm. in 25704 ; of 6 '2 mm., somewhat exaggerated by flattening, in specimen 6. 

 From this they taper to the distalmost portion preserved, which in 25704 has a 

 diameter of \'S mm., in specimen 6 of 1'6 mm. 



The interval between the bottom of the proximal flange and the bottom of the next 

 is circa '75 mm. in 25704 ; in specimen 6 the two flanges are closely apposed, but the 

 normal distance, as measured in the 3rd and 4th flanges, is about I'l mm. and remains 

 the same to the 14th and 15th flanges. In 25704, however, the distance increases, and 

 at the 12th flange is already 1'8 mm. In both specimens the height of both flanged 

 and intermediate columnals continues to increase until a maximum is reached, which 

 in 25704 appears to be 4*5 mm. In the distal region of specimen 6, well-preserved 

 columnals have a height of 3 mm. , and at the swelling a diameter of 2 mm. precisely. 



§ 483. The ornament on the proximal flanges consists of prominent granules, 

 usually in two transverse rows. In specimen 6 these are in vertical series, but in 

 25704 they are not obviously so. Lower down in 25704 the columnals are banded 

 with close-set transverse ridges of granules, some of which granules may be larger and 

 in vertical series. In specimen 6 the vertical ridges thus formed are predominant. 



Thus the columnar ornament presents the same individual variation as in P. Rugeri ; 

 but in both species the granulation and transverse banding are always present. 



§ 484. Comparison of the Holotype (25704 and 6a) with the Paratype (6). — In 

 view of the diff"erences between the two individuals, a careful comparison has been 

 made and is here summarised. 



Outline probably similar. 



Ratio, width : height : : 100 : 63 in holotype. 



: 77 in paratype. 

 The difference partly due to crushing. 

 Proportions of individual plates : 



Holotype. Paratype. 



Plate 5, height '91 of width . . . -85 



Plate 6, ,, 1-14 „ ... ca. 1'5? 



Plate 9, „ 1-19 ,, . . . 1-22 



Obvious structural diff"erence, in extension of plate 7 in paratype ; but the 

 diff"erence may not be so great as it appears (§ 474). 



Ornament, dominance of concentric on both theca and stem in holotype ; 

 of axial in paratype. 



These differences appear quite explicable as individual variations, and are certainly 

 less than those which separate these specimens from those definitely assigned to 

 P. Rugeri. 



§ 485. Comparison of P. anglica with P. Rugeri. — It will have become clear that 

 the differences between the two species are not exactly those on which Dr Jaekel laid 



TKANS. ROY. SOC. EDIN., VOL. XLIX. PART II. (NO. 6). 63 



