PA L.EONTOLOG Y. 73 



MICHELINIA CYLINDRICA, Milne-Edwards. 



Synon., Emmonsia CYLINDRICA, Milne-Edwards. 



MiCHELlNIA INTERMITTENS, Billings in parte. 



Synon., Favosites Maximus, Troost. 



Large, convex masses, formed of slowly diverging, subparallel, 

 obtusely polygonal, sometimes circular tubes of unequal size, from 

 five to seven millimeters in diameter. The tubes have either 

 straight walls, or are at regular, short intervals constricted by ring- 

 like carinas projecting into the tube cavity. The carinse, caused 

 by constriction of the walls, correspond with each other in the adja- 

 cent tubes, but the contiguity of the tubes is usually not inter- 

 rupted by them. The tubes with straight walls are polygonal in 

 outlines; those with constrictions are circular ; transitions from one 

 form into the other are noticeable, sometimes in the same speci- 

 mens. Inner surface of tubes longitudinally striate and densely 

 covered with irregularly dispersed, spinulose projections, which also 

 spread over the surface of the diaphragms. Diaphragms com- 

 pound, of interlaced, vesiculose plates, not near so convex as in the 

 former species, and in close approximation. Lateral pores very 

 irregular, and of different sizes ; in the specimens with constricted 

 tubes they are confined to the dilated parts, interstitial between 

 the annular, projecting carinse. Occurs with the other species in 

 the drift deposits of Michigan ; it is the most common species of 

 the genus at the Falls of the Ohio, and is found in many localities 

 of Ohio and Indiana, 



Plate XXVI. — Fig. 3 gives a side view of a silicified specimen 

 from the Falls of the Ohio. Fig. 4 is a surface view of a large, con- 

 vex mass from the same locality. 



MICHELINIA FAVOSITOIDEA, Billings. 



Convex masses of diverging, intimately united, polygonal tubes, of 

 unequal size, from three to five millimeters in diameter. Basal part 



