and the New Genus P rotistograptus. 57 



the fewness of thecse and the absence of dichotomy. Here 

 apparently a primitive sicula accompanies a primitive genus. 

 On the other hand, the apertures of some of the Diplograpti- 

 dae are more complex, with lobes and spines. 



The species of Protistograptus described below depart from 

 the primitive type of a sicula in their curvature and apertural 

 spine or lobe. These characters exclude them from direct 

 genetic relationship with Corynoides, although that is the 

 nearest known genus in fewness of thecse. P. corrugatus 

 approaches in size the sicula? of Goniograptus perflexilis and 

 G. geometricus, but it is larger and different in form. The 

 siculse of Goniograptus are straight, while those of the known 

 species of Protistograptus are wholly, or in part, curved. 



While Protistograptus is structurally ancestral to all grapto- 

 lites and is found associated with the second graptolite fauna 

 {Dictyonema flabelliforme preceding), it seems probable that 

 the known species depart from the primitive type and are not 

 directly genetically related to any of the known graptolite 

 phyla. 



Protistograptus niinutus (Matthew). 



Cyrtotheca minuta Matthew, Nat. Hist. Soc. New Brunswick, 



Bull. No. 10, 1892, p. viii. 

 Crexeis minuta Matthew, Trans. Roy. Soc. Canada, vol. 10, 



sec. 4, 1892, p. 105, pi. 1, figs, lla-llc. 



" A minute elongated arched cone or sheath, acutely pointed 

 at the apex, near which the shell is more rigid than at the 

 larger end. . . . The outer surface is smooth, except toward 

 the apex where some examples show longitudinal ridges. 

 Under the microscope the surface is seen to be minutely striu- 

 late transversely. . . . Length 4 mm . Width about one-fifth of 

 the length." 



The species may be further described as an arched, rapidly 

 expanding cone. Apertural margin rises in an acute spine. 



A large specimen (see fig. 2a) is 7 mm long, broadly arched, 

 and rapidly expands to an apertural width of l-2 mm . Apertural 

 margin inclined on the concave side at an angle of 120° and 

 on the convex side rises more steeply, forming an acute spine. 

 Carbonaceous layer almost wholly removed. Surface with 

 numerous transverse cracks which are not filled with carbona- 

 ceous matter and are too irregular for transverse diaphragms. 

 Matthew, in his specimens, finds ridges which are " often very 

 regularly spaced and may possibly mark the position of dia- 

 phragms." The writer's specimens do not show these. 



A few small specimens (see fig. 2b) also exhibit the character- 

 istic rapid widening of the sheath, but the aperture is obscure. 

 One of these shows longitudinal ridges, which, however, are 

 due to crushing in the sediment. 



