﻿174 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 5, 



Diplograpsus* bullatus, Salter. Pl. X. fig. 2. 

 Prionotus pristis, Hising. Leth. Suec. Suppl. pl. 35. fig. 5 ? 



Our specimens are not more than 1^ inch long and a line wide. 

 The rachis, which is convex, and puckered or bullate at short inter- 

 vals, is broader than the cell-denticles ; these latter, being the spaces 

 between the cells, are broader and squarer in the young part, but di- 

 minish in breadth upwards as the size of the oblique cell-apertures 

 increases. Our magnified figure shows the apertures too narrow, and 

 the interspaces or denticles consequently too square for the adult por- 

 tion, although this varies considerably in different specimens. On 

 one compressed individual the thin solid axis is visible, but usually 

 it cannot be detected. 



Hall's figures of G. pristis (Pal. N. York, pl. 72. fig. 1) show a 

 convex though not bullate rachis, and do not differ much in general 

 character from ours ; but until a better acquaintance with Hisinger's 

 original species is obtained, it is thought better not to identify these 

 Ayrshire specimens with it. 



Locality. Ardwell and Piedmont Glen. 



Nidtjlites favus, Salter. Pl. IX. figs. 16, 17. 



The fossil to which the above name is applied is a frequent one in 

 the Llandeilo flags of Pembrokeshire ; at Haverfordwest particularly 

 so, where it occurs associated with fossils very much of the same 

 character as those from the strata here described. It occurs as oval 

 or roundish plates, about 2 inches broad, spreading out from a 

 centre (of attachment ?) into a flattened irregularly wavy form ; the 

 entire surface of both upper and under sides covered with hexagonal 

 cups, in our Scotch specimens a line wide, in the Welsh ones something 

 less. These cups are about two-thirds their diameter deep, their 

 edges smooth and even with the general surface, and their bases 

 rounded and almost always with a central punctum or depressed 

 point (which shows itself on the cast as a tubercle), and which is 

 probably its point of attachment to the membrane or lamina form- 

 ing the base for both series of cups. This membrane, whatever 

 may have been its texture, is always absent in our specimens, a nar- 

 row space, as in fig. 1 7 b, being left between the upper and under 

 series of cups, though some traces of its presence are to be seen in 

 some sharp wrinkles which are seen radiating from the centre of the 

 plate where one series is broken away. The lower surface of the 

 cups themselves appear to have been a little wrinkled too towards 

 their pedicle, as may be seen on the specimen fig. 17 a, where one 

 series of cups has been separated from the opposite one before being 

 fossilized, and where we have consequently only the impression of 

 their lower surface. Such an impression has been figured (from this 

 locality) by my friend Prof. M'Coyf, as a cast of his Palceopora 

 favosa. 



* " Barrande's synonym * Diprion' for this genus, is already applied to a genus 

 of insects." — M'Coy in litt. 



f Syn. Classif. Brit. Pal. Rocks, Pt. 2. pl. 1 c. fig. 3 c, d. 



