GRAPTOLITES OF NEW VORK, PART 2 



451 



Description. Rhabdosome obviously very long ; for fragments 80 mm 

 long and without appreciable change in width and others 2 mm wide indi- 

 cate, in view of the slow rate of growth of the rhabdosomes [see fig. 428] a 

 considerable distance of the fragments from the sicular extremit) ; very 



429 



425 



430 



431 



Fig. 425 Monograptus priodon Bronn (x 28). Copy of restoration from Perner, for comparison with 

 M. clin tone n sis and to show structure of rhabdosome of Monograptus. Fig. 426-31 Monograptus 

 clintonensis (Hall). Fig. 426 Copy of one of Hall's figures in Canadian Organic Remains. Fig. 427 

 Mature portion of pyritized rhabdosome, showing form of thecae. Fig. 428 Sicular portion of partly pyritized 

 rhabdosome, showing sicula, recurving of first theca and shape of earlier thecae. Fig. 429, 430 Thin sections 

 through pyritized specimens; figure 429 near surface; figure 430 approximately through median plane. Fig. 431 

 Transverse section of pyritized specimen: I = common canal, II = theca seen from below, HI = nemacaulus and 

 virgula. x 5 



slender and nearly straight, with a short, slight curvature of the sicular end. 

 Width at sicular extremit)- .3 mm ; that of mature parts 2 mm. Sicula 

 small (1.5 mm) and slender; furnished with an apertural spine. First 



of last third of sicula anc 



theca originating' at beginnin 



)ecominsf 



o 



