Vol. 56.] WENLOCK SHALES OF THE WELSH BORDERLAND. 407 



with a long and stout virgella, which is often 1 inch long (25 mm). 

 The rhabdosoma widens rapidly from its origin for the first | inch 

 (12*5 mm.), and then slowly for the remainder of its length. 



Width at origin ^ inch (1*05 mm.). 



Width at \ inch from origin J w inch (1-587 mm.). 



Maximum width T ^ inch (2*1 mm.). 



Fig. 18. — Monograptus nexilis, sp. nov., from Moel Ferna. 



Fig. 19. — M. irfonensis, 

 sp, nov., from the B. 

 Irfon. 



[Nat. size.] 



The virgnla is often prolonged distally, especially in young forms. 

 The thecae are of the normal Fkmingii-ty-pe, and agree with that 

 species in inclination, being inclined to the axis at 40° ; the first 

 thecal aperture is on a level with the apex of the sicula, and the 

 thecae number twenty-two to twenty-four in the inch (eight or nine 

 in 10 mm.). The species is allied to the 

 members of the Flemingii-riccartonensis 

 group, but differs in the amount of 

 curvature of the rhabdosoma and in the 

 presence of the long virgella. 



H o r i z on. — Zone of Cyrtograptus Lin- 

 narssoni, Lapw. 



Localities. — Moel Ferna, Slate 

 Quarries. Stream south of Toinen-y- 

 Meirw. 



Monograptus irfonensis, sp. no v. 

 (Text-fig. 19.) 



Rhabdosoma very slender, rigid, 



h u straight, attaining a length of 8 inches. 



[x5.] [Nat. size.] Sicula small, inconspicuous, -^ inch 



(1-01 mm.) long ; rhabdosoma very 



narrow at the origin, increasing slowly up to a maximum of 



•Jj inch (1-05 mm.). 



Thecae very long and narrow, in contact for half their length, 



