Vol. 56.] FORMATION AND ITS GRAPTOLITE-FAUNA. 459 



Horizon. — It is the characteristic fossil of the M.-tumescens 

 zone near the top of the Lower Ludlow Shales. Eorms almost 

 identical with it, however, occur in the lower zones of the Ludlow. 



Associates. — Monograptus tumescens var. minor, M. chimcera 

 (very rare), M. bohemicus (very rare). 



Var. minor (M'Coy), non Monograptus ludensis. (PI. XXV, 

 figs. 6a & 6 b.) 



1855. Graptolifes ludensis var. minor, M'Coy, 'Brit. Paloeoz. Foss.' p. 5. 



M'Coy described under this name a ' species resembling' M. luden- 

 sis, ' but of only half the width, yet having from four to five denticles 

 in a space of two lines/ I have been unable to obtain specimens 

 from M'Coy's type-locality at Llangynyw Rectory (Montgomery- 

 shire), but from specimens formerly in Nicholson's collection, and 

 now in Prof. Lapworth's possession, I am inclined to the opinion 

 that the form here described is identical with M'Coy's variety. 



M. tumescens var. minor agrees with the typical M. tumescens 

 in 



(1) The character of the proximal extremity ; and 



(2) The shape of the thecse. 



It differs from it in 



(1) Its small size, never exceeding 127 mm. (*5 inch) in length, and 



measuring generally less ; 



(2) The form of the polypary. 



Localities. — Long Mountain (Llettygynfach) ; Ludlow district 

 (Elton-Ludlow Road, Elton Lane) ; Llangynyw Rectory (Mont- 

 gomeryshire). 



Associate. — M. tumescens. 



I have had the opportunity of examining only one of the spe- 

 cimens which Nicholson collected from the Lake District, and 

 described as M. colonus. This is now in Prof. Lapworth's col- 

 lection at Mason University College, Birmingham. Unfortunately, 

 it is by no means well preserved. I have, however, found others 

 very similar in the Ludlow district (Elton Lane, etc.), and the form 

 is evidently closely allied to, if not identical with, the species which 

 I have described as M. tumescens. The Lake District form is 

 shorter and stouter than the typical M. tumescens, and the thecse 

 are more close-set, thirty-three to thirty in the inch (thirteen to 

 twelve in 1 cm.). They may all belong to a distinct variety of 

 M. tumescens, but at present there is not sufficient evidence to 

 decide this point. 



Monograptus comis, sp. nov. (PI. XXV, figs. 8 a & 8 b.) 



Polypary barely 2'5 cm. (-07 inch) in length. Straight for the 

 distal half of its length, curving inward distinctly in the proximal 

 half. Increase in width, from -5 mm. ('02 inch) to 1*27 mm. 

 (-05 inch), gradual throughout the polypary. In the only specimen 

 that shows the distal end, the virgula is slightly produced beyond 

 the terminal theca. 



