84 



BRTTTRH GRAPTOLITBI^. 



liowever, only visible on tlio best preserved specimens, or on tlie more distal 



stipes when these are seen in trne profile. Each 



Fid. W). — Clonograjitns lenellus, 



Linnarsson. tlicca averages 1'5 mm. in length. 



Affinities. — The peculiar character of the distal 

 thec£e in the Shropshire specimens (see Fig. 46) is 

 not clearly brought out in the figures of the Swedish 

 examples of (J. tenellus [loc. cit. sujjva) ; but as these 

 features are seldom seen, being dependent on the 

 mode of preservation, and the Swedish and British 

 forms are identical in other respects, we have no 

 hesitation in referring them to the same species. 

 The example figured on PI. X, fig. 2 r, from Barf, 

 has been referred to G. tenellus with doubt. 

 Horizon and Localities. — Tremadoc. Lower Skiddaw Slates. 

 N. Wales: Tremadoc (P). SlLvopsMre : Mary Dingle ; Conrad Brook (?). Lalce 

 District : Barf (r). 



Associates, etc. — G. tenellus occurs in Shropshire associated with C, var. Callavei. 

 It is one of the earliest Graptolites known to us. It also doubtfully occurs in the 

 Lower Skiddaw Slates of Barf, and in the Tremadoc beds of Wales. Good 

 specimens of the typical form are in the collection of H.M. Geological Survey. 



Distal thccffi in low rolicf. 

 Dingle, Shineton Shales 

 II.M. Geological Survey. 



Mary 

 Coll. 



Var. Callavei (Lapworth). Plate XI, figs. 3 a—c. 



Fig. 47. — Clonograptus Callavei. 

 Lapworth. 



1880. ? Bryograjdvs Callavei, Lapworth, Ann. Mag. Nat. Hist. [5], vol. v, p. 165, pi. v, fig. 21. 



Description. — In addition to the typical form of Glonogrnj^lns tenellus, there 

 occur associated with it in the Shineton Shales 

 examples of a variety, the branches of which are 

 more rigid and much wider. The theca3 are of the 

 same type, but larger and fewer in a given unit of 

 length (eight in 10 mm.). Each theca has an 

 average length of 2 mm. Figs. 3 a and 3 h, PI. 

 XII, show the true characteristics of this variety. 



llemarJcs. — The specimen originally described 

 and figured by Lapworth as Bryograptus Callavei 

 from Mary Dingle, Shineton Shales, has unfor- 

 tunately been lost. There occur, however, at the 

 same locality abundant examples of the special 

 variety of Glonograptus tenellus here referred to. 

 These agree fully in the number and form of the 

 Lapworth's descri])tion, and there can be little oi- no doubt that his 



Distal thecce in low relief. Enlarge 

 nient of PI. XI, fig. 3 a. 



with 



