Vol. 56.] FORMATION AND ITS GRAPTOLITE-FATJNA. 479 



Monograptus Nilssoni and M. scanicus, more especially in the former. 

 In Germany it is found in the Graptolithengestein, in association 

 with other Lower Ludlow forms. 



Associates. — M. bohemicus, M. Nilssoni, M. varians and its 

 variety pumilus, M. dubius, and M. chimcera var. JSalweyi. 



(e) Group 5. Type M. scanicus, Tullb. 



1. Thecas without overlap ; apertures concave, with the upper 

 wall bent into a claw. 



2. Polypary slender, curved. 



Monograptus scanicus, Tullb. (PI. XXY, figs. 25a & 25b.) 



1883. ' Skanes Graptoliter ' pt. ii, Sver. Geol. Undersokn. ser. C, no. 55, p. 26 & 

 pi. ii, fig. 38. 



Polypary slender, slightly curved, very flexible, so that the 

 general form varies constantly. Length of whole polypary not 

 seen; the longest fragments measure 10*1 cm. (4 inches). It is 

 extremely slender at the proximal end, about -254 mm. (-01 inch) 

 in width, widening very gradually, and attaining a maximum width 

 of about 1 mm. (*04 inch) at the distal end. 



Proximal Extremity. — Sicula rarely preserved, but it has 



been seen in a few specimens; about 



Fig. 22.— M. scanicus, l'p mm - (* 06 incn ) in length, while the 



Tullb., from Aberedw width at the aperture is about one- 



Hill(xS). sixth to one-seventh of the length. 



Aperture concave, dorsal wall provided 



with a fairly long, slender spine. The 



first theca arises at a distance of about 



one-third of the length of the sicula 



from the aperture of the sicula. 



Thecae. — Twenty to twenty-three 



in the inch (eight to nine in 10 mm.), 



being more distant at the proximal 



extremity and inclined to the axis at 



an angle of 10° to 20°; generally 



arranged on the concave side of the 



polypary, though occasionally at the 



proximal extremity they occur on the 



convex side. Thecae long narrow 



a b tubes, of equal width throughout ; 



<i=Distal thecae. aperture concave, the upper wall 



b= Proximal extremity, with curving over it in the form of a 



sicula. claw, which is bent outward and 



downward. The aperture resembles 



that of M. uncinatus in shape, but differs markedly in size. At the 



proximal extremity the proportion between the length and width of 



the thecae is about 7 to 1 ; distally it is only 5 to 1. Thecae in contact 



merely, no overlap; the median wall of the proximal thecae is much 



shorter than that of the more distal thecae. 



2k2 



