668 J. HOPKINSON AND C. LAPWOKTH ON THE GRAPTOLITES OF 



DlCTYOGRAPTUS CANCELLATTTS, Hopk., Sp. nOV. PL XXXVI. 



figs. 11a & 116. 



Brit. Assoc. Report for 1872. 



Branches numerous, strong and flexuous, maintaining an equal 

 width throughout ; about twelve in the space of an inch, equal 

 in width to one half the interspaces ; frequently bifurcating, 

 and anastomosing about as often, and connected occasionally 

 by transverse filaments of the same substance as the branches ; 

 fenestrules of a lengthened oval shape, or sometimes approach- 

 ing a rectangular form, somewhat irregular in proportions and 

 disposition, and about three times as long as wide. 



The most distinctive characteristic of this species is that the 

 meshes or interspaces are chiefly formed by the branches coalescing 

 and dividing by virtue of their curvilinear direction, being connected 

 by transverse filaments only here and there where not sufficiently 

 undulated to be brought quite into contact, and not being connected 

 at all where the undulations do not bring the branches into toler- 

 ably close proximity to each other. 



This form differs so widely from the typical species of Dictyo- 

 graptus that it will most probably ultimately be necessary to make 

 it the type of a distinct subgenus, for which the name Desmograptus 

 (ceafxbs, a link) is here proposed. 



Log. Lower Arenig, "Whitesand Bay. 



DlCTYOGRAPTUS IRREGULARIS, Hall, PL XXXVI. fig. 12. 



1865. Dictyonema irregularis, Hall, Grapt. Quebec Group, p. 136, 

 pi. xx. figs. 1, 2. 

 Branches flexuous, frequently bifurcating, about twenty-five in the 

 space of an inch, equal in width to one half the interspaces ; 

 frequently and somewhat regularly auastomosing ; the con- 

 necting filaments of irregular width (usually slender), expand- 

 ing at their junction with the branches, and forming very 

 irregularly-shaped fenestrules, usually longer than wide. 



It is extremely difficult to draw up a rigid definition of this 

 species, the size and shape of its fenestrules varying so greatly. In 

 our specimens the branches seem to anastomose almost as often as 

 they bifurcate, and the connecting filaments form an irregular, 

 usually diagonal line across the branches, which thus divide and 

 coalesce together — a feature shown in Hall's fig. 1, which is the 

 figure our specimens most nearly resemble in other respects also. 

 The fenestrules seem on the average to be about twice as long as 

 wide, and are most usually of an irregularly oval shape. Very 

 decided indentations, circular in form, are seen here and there on 

 the branches. 



Log. Middle Arenig, Whitesand Bay. 



Dictyograptus Homfrayj, Hopk., sp. nov. PL XXXVI. fig. 13. 



Branches numerous, flexuous, radiating in a complete circle from 

 the centre of attachment, or hydrorhiza ; frequently bifurcating, 



