TETRAGRAPTUS. 67 



reudil}^ distill o-nislied from T. /??V/.s-A_/// by its <>-onoral sliapc and the fewer tliccsv in 

 a o'ivcii unit of IcnQ'tli. 



Tlorizon and Loe.nTific^. — Arenig, Middle Skiddaw Slates (Upper bods). 



Lal-e District : Randal Crag ; Bassentliwaite Sand-beds ; Ontersido ; Gibraltar; 

 Great Knot. St. David's : Wliitesand Bay ; north of Talfan, Wliitland. S. 

 Scotland : Bennane Head, Ballantrae. 



Associates, etc. — 7'. sei-ra appears to ho particularly abundant in the Skiddaw 

 Slates, where it occurs associated with T. Amii, D. e.tiensvs, etc. ; it has been 

 recorded by the Geological Survey from the Arenig l)eds of S. Scotland [loc. 

 cit. supra), and is also present in S. Wales, where it is associated with numerous 

 Devdrograjiti. There are good specimens of it in the collections of the British 

 Museum, the Woodwardian Museum, and in Lapworth's private collection. 



Tetragraptus reclinatus, sp. nov. Plate VI, figs. -5 a — c. 



Stipes slioi't, from 12 to 19 mm. in length, approximately straight, directed 



ol)liquely upward, very narrow at origin, and with a uniformly narrow 



width (2 mm.) for the greater part of their length. Sicula conspicuous. 



TliecgG twelve to thirteen in 10 mm., inclined at 45°, three times as long as 



wide, in contact two thirds their length. Apertural margins normal, straight. 



Description. — The stipes grow upward at a wide angle from each other ; those of 



the first order do not exceed 5 mm. in width. Dichotomous division appears to 



take place after the development of tli. 2' and th. 2", though this is uncertain. 



Thereafter the Avidtli of the stipes increases to 2 mm., and this width is maintained 



for the remainder of their length. 



The sicula has a length of about 1*5 mm., and the 



Fio. 41. — Tetraijraptus reclinatus, _ _ ° _ 



nov. first theca originates a short distance below its apex. 



The average length of the thecfe in the distal por- 

 tions of the stipes is 1"6 mm. 

 rroxiiuai end, reverse view. Enlarge- Ajjiuities. — Tetragvaptus rccliuatus rescmblcs T. 



ment of I'l. VI, fio-. 5 a. . , , i , • f it 



scrra, m general shape, but is tar more slender 

 than that species, and thus may be readily distinguished from it ; further there 

 are a greater number of thecfe in the same unit of length. 



Horizon and Localities. — Arenig, Middle Skiddaw Slates. 



Lake District : Whinlatter ; Carlside Edge. 



Associates. — This species has, up to the present time, only been recorded from 

 the Skiddaw Slates, where it is not an abundant form. The best specimens have 

 been collected by Postlethwaite, and are in his collection. 



