THE OTTAWA NATURALIST 



VOL. XXVIII JANUARY, 1915. No. 10. 



CERAMOGRAPTUS RUEDEMANNI 



A New Genus and Species of Graptolitoidea, and Notes on 

 Urasterella pulchella, Billings. Plate II. 



By George H. Hudson. 



The holotype of this species is the fragment of a rhabdsome 

 Iving across the weathered base of an arm of the holotype of 

 Urasterella pulchella, Billings, in the Victoria Memorial Museum, 

 Ottawa, Canada. Horizon — Trenton at Ottawa, Canada. 



This species seems allied to Cactograptus, Ruedemann, but 

 the difference in form and arrangement of the denticles entitles 

 it to generic distinction. Until new material is discovered the 

 diagnosis of the genotype must answer for that of the genus. 

 Ceramograptus ruedemanni, sp. nov. 



The branch measured across from apparent spine tips of 



oppositely placed denticles is 0.26 mm. wide. The denticles. 



are 0.37 mm. long, placed nearly parallel with the main axis, 



and h)ut slightly overlapping. The lower half of the outer 



margin of each denticle makes an angle of about 2 1 degrees with 



the axis of the branch. The middle is gently convex and on 



this ventricose portion there seems to be a short angular or 



spiny process. The upper half of this marginal line is at first 



slightly concave and subparallel with the axis but soon swings 



out in a graceful curve to the point of a short apertural spine. 



The apertural opening is slightly concave and from the tip 



inward measures 0.08 mm. in diameter. These margins appear 



to be slightly thickened or keeled and the apertural margin 



near the axis is slightly folded or vertically ribbed, presenting 



three short ridges which have strongly reflected the light and 



appear as white spots in the photo-micrographs from which our 



plate was made. The appearance of these denticles is that of 



slender and graceful vases with a pouring lip, each vase set 



with its back to the main axis. Hence the generic name from 



Ceramos, a pitcher or vase. 



