CARADOCIAN CYSTIDEA FROM GIRVAN. 521 



Plate VI. 

 (All the specimens on this Plate are in Mrs Gray's Collection.) 



Pleurocystis gibba, §§ 520-534. 



Fig. 64. G177. Anal face. The periproctals for the most part removed, exposing the inner surface of 

 the antanal plates. Nat. size. 



Fig. 65. G177. Antanal face. This shows well the hump in the neighbourhood of pectinirhomb 11-12. 

 Nat. size. 



Fig. 66. Holotype, G172. Antanal face. The hump or bend in the thecal margin, being a region of 

 weakness, has been crushed outwards. Nat. size. 



Fig. 67. Holotype, G172. Viewed from antanal side, but the plates of that face are removed, exposing 

 the interior of the theca. Nat. size. 



Fig. 68. Holotype, G172. Anal face. The periproctals are disintegrated and obscure. Nat. size. 



Pleurocystis quadrata, §§ 501-519. 



Fig. 69. Holotype, G171. Antanal face. The theca incomplete in the lower left-hand comer. 

 Nat. size. 



Fig. 70. Holotype, G171. Anal face, showing the complete thecal outline. Nat. size. 



Fig. 71. Holotype, G 171. Anal face. The rectal lobe, showing the vent (§§ 513-514). x 4| diam. 



Fig. 72. G174. Two thecas. That on the left lies over the other, and is seen from the antanal aspect, 

 but the plates of that face have been removed, exposing the periproctals. Note the rim for the attachment 

 of the periproctal integument, and the linear arrangement of the periproctals in the rectal lobe. The 

 underlying theca on the right exposes the interior of the antanal face. Between the two thecas lies a 

 crushed Orthis (§§ 517, 518). x 2 diam. 



Fig. 73. G142. Antanal face. To show pectinirhomb 10-14. Cf. text-fig. 73. This photograph 

 may at first be a little puzzling because, to bring out the folds, it was lit from the lower left-hand corner 

 instead of from the upper left-hand. x 2 diam. 



Fig. 74. G175. Anal face, showing periproctals and vent (§§ 517, 518). x2 diam. Photograph by 

 F. W. Reader. 



Pleurocystis foriolus, §§ 535-550. 



Fig. 75. G135. Antanal face, x 2 diam. 



Fig. 76. G135. Anal face, showing the elongate rectal lobe (§§ 541, 547). x 3 diam. 



Fig. 77. G213. Antanal face. Towards the lower left-hand corner some of the plates are removed, 

 exposing the periproctals. x 2 diam. 



Fig. 78. G213. Anal face. Most of the periproctals removed, exposing the anterior of the antanal 

 plates. X 2 diam. 



Fig. 79. Holotype, G189. Antanal face. Nat. size. 



Fig. 80. Holotype, G189. Anal face. The periproctals are almost too small to be clear in this figure. 

 Nat. size. 



Fig. 81. G223. Anal face. A few periproctals remain in the rectal lobe. Elsewhere the inner face 

 of the antanal plates is exposed. The adoral plates are clearly shown. Nat. size. 



