CLIMACOGRAPTUS. 203 



the character of the thecae and its complete septum. There is also a great 

 difference in size, Gl. caudatus being a much larger form than either of these 

 species. 



Horizon and Localities. — Hartfell Shales (zone of J). Glingani). 



8. Scotland: Dobb's Linn; Hartfell Spa; Glenkiln Burn; Black Linn; Pied- 

 mont Glen ; Ard well Farm ; Penwhapple Glen ; Tralodden. Ireland: Ballygrot. 



Associates; etc. — Gl. caudatus is a fairly abundant fossil in the zone of Vicranog. 

 Glingani in S. Scotland ; it occurs in association with the zone fossil and 

 Din-ling. Morrisi. 



Collections.— Sedgwick Museum, Lapworth, and the Authors. 



Climacograptus tubuliferus, Lapworth. Plate XXVII, figs. 8 a — d. 



1876. Climacograptus tubuliferus, Lapworth, Cat. West Scot, Foss., pi. ii, fig. 49. 



1877. Climacograptus scalaris var. tubuliferus, Lapworth, (imp. Go. Down, p. 138, pi. vi, fig. 33. 



Polypary 3 — (> cm. or more in length, increasing in width very gradually from 

 07 mm. at the proximal end to a maximum of 2*5 mm., which is thereafter 

 maintained. Sicula visible for about 1 mm. of length, virgella very robust, 

 often 4 mm. long. Thecas twelve to eight in 10 mm., free edge straight 

 or slightly curved in profile view, apertural margins slightly introverted, 

 lying within semicircular excavations which occupy about one-fourth to one- 

 sixth the width of the polypary. Virgula conspicuous, flattened, distally 

 prolonged for 3 cm. or more, often enclosed within a membranous tube or 

 vesicle. 



Description. — The polypary is often of consider- 

 Fios. 134 « and 6. — climacograptus able extent ; the increase in width from 07 mm. to 



tubuliferus, L.apw. 



,, 2"5 mm. extends over a length of 3 cm., so thai 



smaller specimens naturally appear to widen through- 



| out their length. Lapworth states that the polypary 





i|| has parallel margins, but this is only true of the 



distal parts of long specimens. The virgula is pro- 



/' longed for 3 cm. or more beyond the distal ex- 



I' tremity of the polypary, and is commonly enclosed 



,* _ h within a long narrow flattened or tubular vesicle; 



Typical iorm of proximal end, show- 

 ing rod-like virgella. Enlargement this is frequently only visible when it leaves the 

 of part of specimen on same slab as 



Pi. xxvii, figs. 8 a, b, d. polypary, but in other cases the presence of this 



Reverse view. Belcraig Born, Hart- a * 1 .... 



fellShales. Coll. Wood, flattened plate can he made out within the polypary 



itself. 



