V 



58 F. H. Mc Learn — Lower Ordovician 



This species is rare in the Yale collection and occurs chiefly 

 in the lower horizon (A). 



* Protistograptus corrugatus (Matthew). 



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



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

 C resets corrugata Matthew, Trans. Roy. Soc. Canada, vol. 10, 



sec. 4, 1892, p. 105, pi. 7, figs. 12a-12b. 



"A sheath more elongated than the preceding [P. minutus]', 

 it is also larger, straighter, and is traversed by numerous, 

 closely set undulations of the surface, forming rings that fade 



Fig. 2. 



^ 



Fig. 2 a, b. Protistograptus minutus (Matthew). 



a. Large specimen showing aperture. 



b. Younger form. 



Fig. 2 c~g. Protistograptus corrugatus (Matthew). 



c-d. Form with straight apertural region. 

 e-f. More attenuated variety. 

 g. Shows character of aperture. 



out toward the larger end of the shell. Length 10 mm., width 

 about one tenth of the length." 



Study of the Yale specimens emphasizes the following 

 specific characters : An elongated cone, expanding gradually, 

 arched in the apical portion and almost straight and cylindrical 

 in the apertural portion. A variation occurs in which the 

 whole cone is arched and the apical end extremely attenuated. 

 In one or two specimens this extends into what seems to be 

 a short nema. None of the specimens show the " undulations " 

 described by Matthew. 



A large specimen (fig. 2c) is 6 mm. long and 0*4 mm. in width 

 at the aperture, curved in the apical part and straight in the 

 distal portion. Another specimen (fig. 2d) shows a longer 



