224 THE DEVONIAN OF MISSOURI. 



irregularity depending on the degree of development of the lunarium; disposition of the 

 apertures also irregular, in some cases they are nearly touching, in others being as much 

 as .75 mm. apart. Cell walls thin. Interspaces filled with vesicular tissue, vesicles angu- 

 lar, sometimes as large as the apertures but usually smaller. 



A longitudinal section shows the abundant development of the interstitial tissue, 

 and the irregularly shaped cell tubes. The vesicles are irregularly disposed in some 

 places, but elsewhere are more regular and have the appearance of cylindrical tubes 

 divided by septa. 



Remarks — The distinguishing characteristics of this species are the extreme varia- 

 tion in the shape of the cell apertures caused by differences in the amount of develop- 

 ment of the lunaria, and their irregular arrangement. This irregularity in disposition, 

 and the large and numerous vesicles suggests a relationship with Favosites parasitica 

 Hall, but that form is explanate or ramose, while the Little Saline forms are massive. 



Horizon — Lower beds. 



Type specimen No. 27650 Walker Museum. 



Genus Meekopora Ulrich 



Meekopora sp. 



Plate 58, figures 5, 6. 



Description — Zoarium lamellar, explanate, bifoliate; apertures obliquely inclined, 

 apparently toward the distal margin of the branch, uniform in size, regularly spaced, 

 about three occupying the space of one mm., margin of apertures slightly above the 

 interspaces. Lunaria well developed, walls thin. A longitudinal section shows the 

 bifoliate character of the zoarium, and the convex interspaces between the cell apertures; 

 apertures broader than long. Diaphragms lacking. 



Remarks — This form is especially characterized by the well developed lunaria. 

 The fact that no diaphragms are present is peculiar since the presence of these struc-. 

 tures is mentioned in the description of the genus. 



Horizon — Upper beds. 



Figured specimen No. 27652 Walker Museum. 



Order Trepostomata 

 Suborder Amalgamata 



Family Heterotrypidae 

 Genus Heterotrypa Nicholson 



Heterotrypa undata sp. nov. 



Plate 58, figures 7, 8. 



Description — Zoarium ramose* branches bifurcating, their diameter about 20 mm. 

 Zooecial apertures irregularly disposed, varying somewhat in size and shape, generally 

 polygonal in outline, 3 to 4 occupying the space of 1 mm. Walls thick. Mesopores 

 numerous, exhibiting considerable variety in size and shape and having no definite order 

 of arrangement. A longitudinal section shows the mesopores to be well developed in 

 the mature portion of the zoarium, but absent in the younger. The zooecial tubes grow 

 upward from the base, then bend sharply outwards almost at right angles. Numerous 

 diaphragms cross the zooecial tubes in the mature region, for the most part disposed 

 irregularly, and in a few cases concave downward. Mesopore walls commonly undu- 

 lating. Small, scattered, acanthopores are present. 



