CLIMACOGRAPTUS. 211 



Wales : Rhayader; Pennant Valley. Lake District : Skelgill (?). 



Associates, etc. — CI. extremus, according to Dr. H. Lap worth, is the commonest 

 fossil at the base of the Rhayader Pale Shales, where it is associated with M. 

 crassus, M. pardus, and M. Becli. The type specimens are in his collection. 



Climacograptus minutus, Carruthers. Plate XXVII, figs. 12 a — c. 

 1868. Climacograptus minutus, Carruthers, Geol. Mag., vol. v, p. 132, pi. v, figs. 10 a, b. 



Polypary less than 1 cm. in length, having a maximum width of 1 mm. 

 attained by gradual widening from origin. Sicula visible for 0*5 mm. of 

 its length, which is about 1 mm. Virgella slender but conspicuous, having 

 a length of 1 mm. Virgula distally prolonged. Thecse sixteen to twelve 

 in 10 mm ; alternate, having a length of about 1 mm. and overlapping for 

 half their extent ; apertural margins situated in shallow sub-elliptical 

 depressions occupying about one-third of the total width of the stipe. 



Description. — The polypary commonly measures about G or 8 mm. in length, 

 and widens within the first 5 mm. to its maximum 



Fiu. 142. — Climacograptus minu- • -1,-1 « 1 •, • iij.no • l 



tus, Carr. width of 1 mm. ; it is only about o mm. wide near 



its origin. 



Details respecting the thecse are somewhat uncertain ; 



j the free edge is straight and rectangular in profile 



Proximal end. Enlargement of view > and the apertural margins are then horizontal, but 



xxvi'i "n' '" 7-"'(— lab as P1 " wnen seen m an y other aspect they appear somewhat 



oblique. 



Affinities. — The type specimens of CI. minutus present a striking resemblance 



to compressed specimens of CI. Hughesi, though in their unsatisfactory state of 



preservation it is not possible to state definitely that they are the same, and the 



species is therefore provisionally retained. 



CI. minutus is closely allied to Gl. brevis in point of size and in the general 

 characters of the thecae, but while in CI. minutus the thecal apertures are alternate, 

 in CI. brevis they are opposite and somewhat wider. 

 Horizon mid Localities. — Lower Birkhill Shales. 



8. Scotland : Dobb's Linn, Moffat; Frencbland Burn. Loire District : Skelgill 

 (Dimorphog. confertus zone). Ireland : Coalpit Bay, Donaghadee. 



Associates, etc. — CI. minutus is a rare fossil in the lower beds of the Birkhill 

 Shales, where it occurs in association with Dimorphograptus Swanstoni, ;i charac- 

 teristic fossil of the zone of Diplog. vesiculosus. It also occurs in the Stockdale 

 Shales (confertus zone) associated with Dimorphog. Sioanstoni and the zone fossil. 

 Carruthers' typo specimens, from which the above description was drawn up, are 



