480 DR F. A. BATHER. 



stress. The number of periproctals in P. anglica, for instance, instead of being five 

 times as great, is actually the same as the number in P. Rugeri. I have therefore 

 made a minute comparison of each specimen of P. anglica with the corresponding view 

 of the holotype of P. Rugeri. It is not necessary to print this here because the facts 

 have been given in the descriptions, and attention has already been directed to some 

 of the differences. The conclusions reached are the following : — 



(a) No weight can be attached to minor differences of ornament, which are only 



differences of degree. 

 (6) Differences of anatomical structure, such as the absence of a pectinirhomb and the 

 apparent extension of plate 7, may conceivably be individual abnormalities ; 

 on the other hand, it is noteworthy that a difference in such features does 

 coincide with a different geographical distribution so far as is known at 

 present, 

 (c) There remain differences of general form and of proportion in the plates, such 

 as have proved fairly constant in the American species. In these respects the 

 two individuals from Bardahessiagh agree with one another, and are therefore 

 to be regarded as conspecific. In the same respects they disagree with the 

 holotype of P. Rugeri, and may therefore be placed in a separate species. 

 But, though the two species are best regarded as distinct on the evidence avail- 

 able, they present many points of similarity. In both (a) the periproctals are small, 

 (6) the pectinirhombs are widened across the sutures, (c) the general character of the 

 ornament is the same, and {d) the main thecal plates are relatively wider than in 

 the Canadian species. 



It may therefore be that the differences between the original specimens are a 

 consequence of structural abnormalities, and that future material will prove all to 

 belong to a single species. 



Comparison with other Species. — See further %l 551-553. 



Pleurocystis procera n. sp. 

 (PI. V. fig. 63. Text-fig. 72.) 



§ 486. Diagnosis. — A Pleurocystis with outline elongate [not seen in lower partj ; 

 shoulder-angle ca. 70° ; ratio, width : height, of theca, 78 ; of plate 5, 74 ; plate 3 

 descends below second fiange. Pectinirhomb 1-5 suppressed; 10-14 widened, kite- 

 shaped, fiat, with slight border ; folds on 14 probably covered ; 11-12 small, triangular. 

 [Anal face not seen.] Ornament of antanal face, granules in concentric lines, main 

 axial ridges fine but distinct. Columnal flanges granulate. 



§ 487. Locality. — Thraive Glen, Girvan. 



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



§ 489. Holotype. — The unique specimen Gl44. 



