402 



MISS G. L. ELLES ON THE WENLOCK [May 190a, 



Description of the Species. 

 1. Genus Monograptus, Geinitz. 

 Monograptus Flemingii (Salt.). 



Salter, Quart. Journ. Geol. Soc. vol. viii (1852) p. 390 & pi. xxi, figs. 5 a-b, 6, 7 a-b ; 

 Lapworth, 'Scottish Monograptidse ' Geol. Mag. 1876, p. 504 & pi. xx, fig. 8 ; Tullberg, 

 ' Skanes Graptoliter ' pt. ii (1883) Sver. Geol. Undersokn. ser. C, no. 55, p. 23 & 

 pi. ii, fig. 25. 



Borne of the forms originally united by Salter under this title have 

 been separated by Lapworth as M. riccartonensis ; those in which 

 the rhabdosoma was broadest and the thecae more numerous were 

 retained as M. Flemincjii. Good descriptions of these forms are 

 given by Lapworth and Tullberg (op. cit.) They are allied to 

 M. priodon (Bronn), but may be readily distinguished from that 

 species by the backward curvature of the proximal end and the 

 character of the thecal apertures. 



In my work among the Wenlock Shales I have found that there 



are four different varieties of this species, which are characteristic 



of different horizons, and these I have 



Pig. 11. — M. Flemingii, called in my lists of fossils vars. a, /3, y, 



var. a, from Dulas Brook t), denoting the order of their appearance. 



and Nant Prophwyd. The chief difference in the varieties is 



usually to be found at the proximal end. 



Var. a. (Text-fig. 11.) 

 Greatest length observed = 1| inches 

 (37*5 mm.). Common form only | inch 

 (17'6 mm.) long. Length of sicula 

 = X- inch (1-587 mm.). Outer wall 

 decidedly curved, giving the appearance 

 of a backward curvature to the extreme 

 proximal end of the rhabdosoma ; 

 inner wall straight. Yirgella directed 

 obliquely backward. Thecae varying 

 in number in different parts of the 

 rhabdosoma, for first J inch = thirty-six 

 to the inch (fourteen in 10 mm.), first 

 ^ inch twenty-eight (eleven in 10 mm.), 

 | inch twenty-four (nine in 10 mm.), 

 1| inches twenty (eight in 10 mm.); 

 narrow proximally, but increasing 

 steadily up to a maximum width of 

 -Jq- inch (2-54 mm.). Virgula not distally 

 prolonged. 



Var. /3. (Text-fig. 12.) 

 Closely allied to the foregoing, but the whole of the proximal end 

 has a decided curvature, both the inner and outer walls of the sicula 

 being curved. 



Var. y. (Text-fig. 13, p. 403.) 

 A small compact form, very rarely exceeding 1 inch in 



[Nat. size.] 



Fig. 12. — M. Flemingii, 

 var. (3,from Dulas Brook. 



[Nat. size.] 



