90 Cincinnati Society of Natural History. 
constituting the clusters or “macule’’ being separated from each 
other by rather thin walls. The large spiniform tubuli are distinct 
enough, but the smaller ones can not always be detected. Especially 
is this the case in examples taken from a shaly matrix. In other 
specimens they are more apparent. 
Longitudinal sections (PI. I., fig. 40) show that diaphragms, with 
an occasional exception, are entirely absent in the axial region, where 
the walls of the tubes are also very thin. The tubes approach the 
surface in a gradual curve, and as they enter the peripheral regions, 
their walls are thickened, sometimes becoming slightly beaded. Very 
thin straight diaphragms are developed crossing the tubes at distances 
apart of from one to one third tube diameter. The interstitial cells 
are divided by diaphragms, only a little more crowded than those in the 
proper zooecia. The large spiniform tubuli make their first appearance 
in the axial region, and.in their course to. the surface, they frequently 
cross obliquely over the tubes (see figure). The smaller ones are first 
developed in the “mature” or peripheral region, and can always be 
seen when the section passes through the face ofa tube. The figure 
on Plate I. represents two tubes so divided. 
In transverse sections the tubes in the central portion of the branch 
are slightly larger than nearer the margin. The walls are excessively 
thin, and polygonal, often nearly circular. Numerous smaller and 
more angular cells (young) occupy the interspaces left between them. 
The margin of the section cuts the tubes longitudinally, where they 
have the same appearance as in the peripheral regions of a vertical 
section. 
Dekayella is probably more nearly allied to Dekayga than to any 
other genus of the Monticuliporide. On the other hand the cell struc- 
ture slightly resembles that of Heterotrypa. From the former the new 
genus is separated by having the tube-walls in the “ mature” region of 
the zoarium thicker; in having numerous interstitial tubes, and in- 
stead of one, two distinct sets of spiniform tubuli. From Heterotrypa, 
Dekayella is distinguished by its ramose growth, and two sets of 
spiniform tubuli. The most peculiar character of the genus is found 
in the two sets of spiniform tubuli, differing from each other, both in 
the time of their development, and size. The larger set are precisely like 
those of Dekayia, and, as is likewise the case in that genus, they make 
their appearance already in the axial or “immature” region of the zo- 
arium. This fact seems to point to a considerable difference in the 
functions of the two sets. The smaller spiniform tubuli are precisely 
°— a ee 
