478 DR F. A. BATHER. 



ance recalling Salter's description of P. Rugeri (§ 454) and evoking a suspicion that 

 he may have seen this specimen. The explanation of the appearance probably is that 

 plate 1 has been squeezed out of sight and covered by plate 2. 



§ 478. The elongate ellipses of the upper pectinirhombs are seen in 25704, and at 

 most twelve folds can be counted in rhomb 10-14 (text-fig. 70). Dr Jaekel says of 

 specimen 6 "das obere [Porenfeld] auf 1'3 : I'i breit"; but, though the statement is 

 probably correct, I am unable to confirm it from the present evidence of the specimen, 

 since the rise of the umbones of plates 1 and 1 1 to form the borders of the rhombs is 

 all that can be seen. 



§ 479. The Periproctals, as seen in 6a, are markedly, though not quite regularly, 

 hexagonal, with a faint concentric ridging. Those near the middle region are generally 

 the larger, some with a diameter as much as 1 mm., but some smaller ones are inter- 

 calated. Near the frame they are smaller, running 4, or even as many as 9, to the 

 square millimetre. 



The diameter of the periproct is about 20 mm. near the base, and continues at this 

 width to a height of about 12 mm. The total area may be estimated at 360 sq. 

 mm., and, taking an average of 3 plates to 1 sq. mm., one obtains a total of 1080. 

 Dr Jaekel's estimate is 1500. Splitting the difference gives 1290, which is very close 

 to our estimate for P. Rugeri, viz. 1200. 



§ 480. Dr Jaekel's drawing of the plates round the Vent is a restoration, which, 

 however correct, is unsupported by evidence. 



§ 481. The Ornament on the antanal face is slightly different in the two 

 individuals. In specimen 6 (PI V. fig. 60) it consists of granules, 9 to 1 sq. mm., 

 arranged in definite axial rows and in less definite concentric rows. In some of the 

 axial rows the granules may fuse to form thin, but prominent and sharply cut, main 

 axial and rhomb ridges, and in most of the plates the granules also fuse to form rather 

 broader ridges radiating from the umbo to the angles. Compared with P. Rugeii, the 

 granules are coarser, the concentric lineation more subordinate to the very definite 

 rhomb lineation, and the ridges are more prominent. 



In 25704 (PI. V. fig. 61) it is the concentric ornament that predominates; it 

 consists of faint, slightly curved ridges, which cross the flattened ridges that radiate 

 to the angles. 



In both specimens the border of the antanal face is slightly swollen, and stiffened 

 by stronger folds parallel to the border and crossing the sutures. The concentric 

 ridges of 25704 as they cross these folds are broken into granules. 



On the anal face, in 6« (PI. V. fig. 62), plates 2 and 3 are strongly marked with 

 fine granular ridges parallel to the sutures. 



§ 482. The Stem in general character is like that of P. Rugeri. In 25704, at 

 least 61 mm. are preserved, but in four separate lengths somewhat disarranged (PI. V. 

 fig. 61). In specimen 6 it is preserved in two main pieces to a length of 86 mm. 

 (PL V. fig. 60). 



