CARADOCIAN CYSTIDEA FROM GIRVAN. 481 



§ 490. Description of Holotype. — The outline is not clearly seen in the lower part 

 of the theca, but appears not to have been quadrate. An elongate appearance is 

 produced by the relatively small shoulder-angle, ca. 70°. 



Height of theca, 16'6 mm. ; width, 12"8 mm. 



§ 491. Plate 5 has a height, 6 '2 mm. ; width, 4 "6 mm. It is hexagonal, that is to 

 say, not reached by plate 2 or by plate 7 ; nor does it seem as though any large extent 

 of plate 7 can have been visible on the antanal face. 



§ 492. Plate 3 descends to below the second flange, but, since the columnals are 

 somewhat shifted apart, the precise level is uncertain. 



§ 493. Pectinirhombs. There is no trace whatever of 1-5, although the tract 

 it would naturally occupy is clearly seen. Considering the absence of this rhomb in 

 P. Rugeri, and the diminution of the other rhombs in this specimen, there is no reason 

 for regarding this as an individual abnormality. 



§ 494. Pectinirhomb 10-14 (text-fig. 72) is kite-shaped, with the long axis across 

 the suture, and the obtuse angle of the kite on plate 10 ; the folds on the outer part 

 of 14 probably covered or closed with stereom (one has to say "probably" when 

 inferring such a character from a single imprint) ; margin slightly raised ; pore-field 

 on 10 rather flat, with apparently only 8, and certainly not more than 10, folds. 



§ 495. Pectinirhomb 11-12 appears as no more than a small triangle, with raised 

 border, and about 5 folds. Whether this represents the actual shape of the complete 

 rhomb is uncertain ; but in any case it was greatly reduced. 



§496. Brachioles preserved to a length of 14 mm.; the more distal of the 

 preserved brachiolars are slightly tumid. 



The anal face is not seen. 



§ 497. Of the Stem four flanges are preserved ; these bear each about two transverse 

 rows of distinct, alternating granules. The intermediate columnals are faintly granulate. 



§ 498. The Ornament of the antanal face is markedly granular. The granules are 

 in definite concentric rows ; and the rhomb-ridges are reduced to thin but distinct 

 main axial ridges. 



§ 499. Comparison with other Species. — In founding a new species on a single, 

 none too perfect specimen, detailed justification is called for. 



Taking first the Girvan species, we note that P. procera diff"ers from P. foriolus 

 and P. gihha in the widening of pectinirhomb 10-14. From P. quadrata, with which 

 it agrees in this respect, it seems to diff'er in the greater relative size of that rhomb 

 and the smaller absolute number of folds. Those features are rather obscure in the 

 specimens, but the absence of rhomb 1-5 and the greater reduction of rhomb 11-12 in 

 P. procera aff'ord more obvious distinction. P. quadrata, moreover, is markedly 

 subquadrate or quadrate, and has a much larger shoulder-angle ; it also has more pro- 

 nounced rhombic and radiate ornament, but on this I lay no great stress. All these 

 differences preclude reference of G 144 to any other Girvan species. 



500. Undoubtedly P. proceiri is nearer to P. anglica and P. Rugeri, closely 



