. Bulletin - New York State Museum. Science. BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 49I Observations. This species is characterized as a primitive Actinoceras by the confinement of the fiUing of the siphuncle to the apical and middle portions. The thickening of the septa around the siphuncle observed here occurs also in Paractinoceras can- ad e n s e Whiteaves. C . b o y c i i has in the depth of the cham- bers, the depressed form of the conch and the nummuloidal char- acter of the siphuncle some similarity to Cyrtoceras sub- turbinatum Bill, from the Lower Siluric of the Mingan i
. Bulletin - New York State Museum. Science. BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 49I Observations. This species is characterized as a primitive Actinoceras by the confinement of the fiUing of the siphuncle to the apical and middle portions. The thickening of the septa around the siphuncle observed here occurs also in Paractinoceras can- ad e n s e Whiteaves. C . b o y c i i has in the depth of the cham- bers, the depressed form of the conch and the nummuloidal char- acter of the siphuncle some similarity to Cyrtoceras sub- turbinatum Bill, from the Lower Siluric of the Mingan islands, but differs in the subcentral position of the siphuncle and- greater curvature of the conch. Cyrtactinoceras champlainense sp. nov. Plate 34, figure 3 ; plate 36, figures i, 2 Description. Conch a small, but slightly arcuate cyrtocera- cone, which expands moderately, the transverse diameter increasing within a length of 20 mm from 9 mm to 15 mm in one specimen; the rate of expansion itself increasing somewhat from the nepionic part of the conch to the ephebic. The largest specimen observed measures 44 mm with the greater portion of the living chamber and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original New York State Museum; New York State Museum. Albany : New York State Education Dept
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectscience, bookyear1887
