Originally: Endoceras inaequabile
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Map point data provided by iDigBio.
- C5 Sequence (Lower Whitewater, Waynesville)
- C4 Sequence (Arnheim)
- C3 Sequence (Mt. Auburn, Corryville)
- C2 Sequence (Fairview)
- C1 Sequence (Clays Ferry/Kope)
Identification in Hand Sample
- Siphuncle straight up one side, very large in respect to shell size
- Endocones located in the apical part of the siphuncle
- Distinguishable form Treptoceras by the much larger siphuncle
- This species is founded upon the siphuncle, all other parts being unknown. The siphuncle is straight up one side. It commences at a point and rapidly swells upon one side for the distance of about an inch, and the slowly contracts itself upon that side until it forms a true cylinder, forward of which, as far as our specimen is preserved, which is more than an inch, there is neither expansion nor contraction. The marks of the septa, upon the cylindrical part, are distant about half the diameter of the siphuncle, cross it diagonally, and inclining forward, upon the straight side, at an angle of about 30 degrees. If we judge by the inclination of the septa, in comparison with the other species, the straight side will be the dorsal, and the distended side, the ventral. Having three specimens of this peculiar siphuncle, I have no doubt that it is a normal form and represents a particular species, though it would have been more gratifying, if the specimens had shown other characteristics in addition to those defined.
- Endoceras inaequabile was described by S.A Miller from the Richmond group at Bristol, Illinois. It consists of the lower end of the siphuncle, showing the impressions of the septal necks as far as the tip, indicating that the neopionic bulb had been completely incorporated into the phragmocene. These impressions are inclined away from the apical end and toward the straight side of the nepionic part of the siphuncle.