DIPLOGRAPTUS. 269 



Catherine's Bridge, Haverfordwest ; Llandewi Velfrey ; Trelydan Dingle, 

 Welshpool. Ireland : Bally grot; Coalpit Bay. 



Associates, etc. — A. perexcavatus is a very abundant fossil in the Glenkiln 

 Shales of S. Scotland and Wales, where it occurs associated with Nemag. gracilis, 

 Dicellog. sextans, Glyptog, teretiusculus var. euglyphus, Glimacog. Scharenbergi, Gl. 

 bicomis, Gl. peltifer, etc. ; it also occurs, but not so abundantly, in the zone of 

 Glimacog. Wilsoni, at the base of the Hartfell Shales, where it is found with Gl. 

 Scharenbergi, Gl. bicomis, and Gl. Wilsoni. 



Collections. — Lapworth and the Authors, Geological Survey of Scotland, 

 Sedgwick Museum. 



Diplograptus (Amplexograptus) confertus (Lapworth). Plate XXXI, figs. 18 a — e. 



1875. Climacograptus confertus, Lapworth, Quart. Journ. Geol. Soc, vol. xxxi, p. 655, pi. xxxiv, 



figs. 4 a—f 

 1880. Climacograptus confertus, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 169, pi. iv, figs. 



15 a — c. 



Polypary characteristically small, rarely exceeding 2*5 cm. in length, and 

 having an average uniform breadth of from 1 — 2 mm. Sicula 1 mm. (?) 

 in length. Thecae sixteen to twelve in 10 mm. ; in obverse aspect, with wide 

 pouch-shaped excavations, declined towards the axis and occupying one 

 third the breadth of the polypary ; in reverse aspect, ventral margin rounded; 

 apertural margin concave and oblique, denticle sharp. 

 Description. — The polypary varies very much in size. An average specimen 

 is about 2 cm. in length and has a width of 1*5 mm., but small specimens having a 



length of 1 cm. and a breadth of 1 mm. are not 



Pigs. 185 a — c. — Amplexograptus confer- n . „ 



tus (Lapw.). uncommon, and occasionally examples are round 



i , ' , ■-.-, which measure as much as 4 cm. in length and are 



j^ j Mi ;-* N S'J 2 mm. wide. There is a slight diminution in the 



Mf \^\ "i width of the polypary towards the proximal end, 



< fefe r '\ but its margins are parallel for the greater part of 



"*f K .;'' its length. 



h c The sicula is rarely seen, but it appears to have 



a. Fragment of proximal end, obverse nad a length of about 1 mm., and the virgella is 



ffiSk£lh£r&pSrSS Slender but conspicuous. Th. 1* originates near the 



Geo? ( We° f of^En" l'anf^nd a P eX ° f the si(3llla alld g rows down to tlle aperture 



Wales before bending outward and slightly upward. Both 



b. Proximal end, reverse aspect. En- ° o ■/ i 



largement of part of one of speci- th. I 1 and th. I 3 possess sub-apertural spines. 



mens figured on PI. XXXI, fig. 18 d. . 



c Distal thecae, obverse aspect, showing The thecas number sixteen to twelve in 10 mm. ; 



deep and oblique excavations. En- 

 largement of part of PL XXXI, fig. they have an average length of 1 mm., and, in the 



18 e. 



obverse aspect of the polypary, exhibit the sharp 



