138 Lapworth — Graptolites of Co. Down. 



which are usually referred by palaeontologists to this species, all agree in the 

 possession of a tapering polypary, destitute of proximal ornamentation; perpen- 

 dicular, short, square, hydrothecse; and straight, or very gently undulating 

 suture. 



59. Var. a. tectus. Barrande. (Grapt. de Boheme. PL 1, figs. 

 19 and 20.) 



Virgula never distally prolonged. Locality — Rare in the Gala Group of 

 South Scotland, unknown as yet in County Down. 



60. Var. b. normalis. Lapw. PI. 6, fig. 31. 



Polypary with sub-parallel margins. Virgula greatly prolonged distally. 

 Locality — Abundant in Coalpit Bay. 



61. Var. c. Climacograptus rectangularis. M'Coy. PI. 6, fig. 32. 

 Virgula prolonged, proximally only, to a considerable length. Polypary 



tapering. Locality — Unknown in Ireland. Rare in the Birkhill Shales of 

 Moffat. 



62. Var. d. Climacograptus caudatus. Lapw. PI. 6, fig. 34. 

 Polypary tapering, several inches in length, with stout virgula prolonged 



both proximally and distally to a length equal to that of the polypary itself. 

 Locality — Unknown in Ireland. 



63. Var. e. Climacograptus tubuliferus. Lapw. PI. 6, fig. 33. 

 Polypary with parallel margins, virgula distally prolonged and expanded 



into a long flattened plate or vesicle. Locality — Carnalea. 



In Scotland each of the foregoing forms has a definite range in the 

 succession of Silurian deposits. They are all most certainly very intimately 

 allied, but it is possible that we may eventually be forced to look upon them 

 as distinct species. Such of these forms as are known upon the Continent have 

 a corresponding vertical range, and appear to possess similar external 

 features. 



64. Sp. 2. Climacograptus Scharenbergi. Lapw. PI. 6, fig. 36. (Catl. 



West. Scott. Fossils. Plate 2, fig. 36). 



Polypary diprionidian, about an inch in length and one-twelfth of an inch 

 in average diameter; proximal end ornamented with a short radicle 



