24 The American Geologist. January, i9o;j. 
which open into rhombic or subelhptical vestibules ; Vestibules 
in very young- specimens subcUiptical. The intersecting series 
and vestibules are not plainly shown in old forms. 
These brief notes may show that the so-called rhombic 
vestibule has l)een overestimated as a character. Probably 
the encrusting form has been described as a species under 
Stenopora. The systematic position of the species is held in 
dispute. Meek placed it under the polypi. 
Position and locality. — Coal Measures : "A rather common 
species at various localities in Nebraska, Kansas, Missouri, 
Iowa, Illinois, and Ohio." Found at Bennett, Roca, Ashland, 
South Bend, Louisville, Richfield, Cedar Cred-c, Plattsmouth, 
Wyoming, Nebraska City. Tecumseh, Table Rock, Humbolt, 
Dawson, Salem, Falls City, Weeping Water, Nehawka and 
other localities in Nebraska. The young form occurs in large 
numbers at Tabic Rock, while the old forms are even more 
plentifully found just above a thick bed of flinty limestone 
outcropping along the Platte river from Louisville to South 
Bend. Permian : Some years ago professor Knight collected 
specimens at Blue Springs and Wymore and referred them 
with question to this species. Since that time the writer has 
identified the species in the Florence flint at those places. 
Professor Prosser has collected and identified specimens from 
the Permian of Kansas. 
EXPLANATION OF FIGURES- 
Young form outlined natural size. 
Young form, transverse section, outlined natural size. 
Old non-montiferous form, outlined natural size- 
Old non-montiferous form, outlined natural size. 
Old montiferous form, outlined natural size. 
Old montiferous form, transverse section, outlined natural size. 
Young form, surface enlarged, showing vestibules with large 
acanthopores at the vestibule angles. 
Old non-montiferous form, tangential section from mature region. 
Young form, transverse section of zoarium. 
Young form, vertical section showing transition from immature 
to mature region as well as form and size of cells. 
II. Old non-montiferous form, vertical section showing walls, tab- 
ulae, and cells. 
Note. — Figures 9, 10 and n were drawn by Miss E. P. Hensel. 
