Mr. C. Lapworth on new British Graptolites. 157 



supra) as to preclude any extended notice in this place. I 

 formerly regarded it as the type form of Hisinger's Graptolithus 

 Sagittarius. The Swedish form to which Hisinger erroneously 

 applied this title proves to be identical with my vax.jaculum. 

 The two forms united by myself under Carruthers's title are 

 very distinct, the younger form differing from the older not 

 only in the angle of inclination and the form and amount of 

 overlap of the hydrothecse, but also in the curvature and the 

 greater diameter of the polypary. It may eventually be 

 shown that they are distinct species. Meanwhile the younger 

 form may conveniently be distinguished as var. nudus. 



Horizon and Locality. M. Hisingeri, Carr., var. nudus , is 

 rare in the Gala group and in the Grieston shales and Kiccar- 

 ton beds of the south of Scotland, the Tieveshilly beds of 

 county Down, and the highest zone of the Coniston mud- 

 stones of Westmoreland. 



12. Monograptus Salteri, Lapworth (non Geinitz). 



Monograptus Salteri (Gein.), Lapworth, Geological Magazine, 1876, 

 pi. x. tig. 8, a, b. 



The fragmentary Graptolites for which Prof. Geinitz sug- 

 gested this specific title (' Die Graptolithen,' s. 36) , were col- 

 lected by Mr. Salter from the rocks of Piedmont Glen, near 

 Girvan (Quart. Journ. Geol. Soc. vol. xii. p. 173), and were 

 originally referred by him to Monograptus tenuis (Portlock). 

 I have recently ascertained that the whole of the strata visible 

 in Piedmont Glen are of Bala age, and therefore of a geolo- 

 gical date anterior to that of the advent of the family of the 

 Monograptidas. Forms of Leptograptidaj are rare in the 

 rocks of the glen ; and these, and not true Monograptida?, 

 were almost certainly the enigmatical examples noticed by 

 Salter. Some well-preserved but fragmentary Leptograptidse 

 from the typical locality of Piedmont Glen, near Girvan, 

 occur in the Hugh-Miller collection, preserved in the 

 Museum of Science and Art, Edinburgh. They are labelled 

 u Graptolites tenuis , Portlk.," and may have been the origi- 

 nal specimens figured by Salter himself. The variation in 

 the curvature of the figured specimens pointed out by my- 

 self is thus naturally accounted for — the Leptograptidas being 

 excessively slender and flexuous, varying greatly in the 

 amount and the direction of their curvature under the most 

 trivial extraneous influences, while among the Monograptidas 

 the curvature of the polypary is so constant in character 

 and direction that it may be safely regarded as a specific 

 peculiarity. 



It is thus certain that the Graptolite to which I applied the 



