126 Cephalojwda of the Cineinnati Group. 



Orthoccras iMeeJci — (S. A. Miller). 



Fig. 12.— Orthoceras Meehl. Longitudinal section, sliowing siphuncle. 



Shell medium size, gradually tapering ; septa moderately arclied, 

 and distant about one seventh the diameter of the shell; siphuncle 

 excentric, or crossing from one side to the other, and conr^isting of a 

 scries of elongate ovate enlargements in each chamber. The greatest 

 diameter of the siphuncle is usually about one half the distance be- 

 tween the septa. The exterior shell and body chamber unknown. 



It is here to be observed that in this species the distance between 

 the septa does not always increase as the shell enlarges toward the 

 anterior end, but sometimes one, two, or three chambers will be narrower 

 than their predecessor. Take a number of them, however, together, 

 and a gradual enlargement of the chambers and increased distance 

 between the septa, as the shell increases in diameter, becomes apparent. 



Found on the hills back of Cincinnati ; range unknown. 



Specific name given in honor of Prof. F. B. Meek. 



Orthoceras Bijrnesi — (S. A. Miller). 



Fig. 13. — Orthoceras Byrnesi. Longitudinal section, showing sipbunclo. 



Shell medium size, very long, and slowly tapering ; arch of the 

 chambers about equal to the distance between the septa, and distant 

 about one seventh the diameter of the shell ; siphuncle excentric, or 

 crossing from one side to the other, and consisting of a series of slightly 

 ovate enlargements in each chamber. The greatest diameter of the 

 siphuncle is, as much or a little more than the distance between the 

 septa, while the septa are pierced Avith. holes about two thirds the 

 diameter of the siphuncle. 



