Revision of Bryozsoan Genera.—Cumings. 201 
‘macule.’ Spiniform tubuli of two kinds; large ones arranged as in 
Dekayia, and a much greater number of small ones. Diaphragms in 
both sets of tubes straight.” The type of this genus is D. obscura. 
On page 90 (Ibid., vol. VI.) the following observations on 
Dekayella are given: 
“Dekayella is probably more nearly allied to Dekayia 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 Hetero- 
trypa, 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 their time of development, and in size. The larger set are 
precisely like those of Dekayia, and, as is likewise the case in that 
genus, they make their appearance in the axial or ‘immature’ region of 
the zoarium. This fact seems to point to a considerable difference in 
the functions of the two sets. The smaller spiniform tubuli are pre- 
cisely like those of Heterotrypa, Amplexopora, and other genera of 
the Monticuliporidae, in which these structures exist, and in none of 
these do they appear before the zoarium has become fully matured.” 
In Eastman’s translation of Zittel’s Grundzuge der Paleon- 
tologie, 1899, the following brief diagnosis of Dekayella is 
given (p. 273): 
“Ramose, branches sometimes compressed. Mesopores more or 
less numerously distributed among the zocecia. Acanthopores of two 
sizes, the smaller ones the more abundant, and present only in the 
peripheral region.” 
Nickles and Bassler include in this genus five species and 
five varieties from the Trenton and Cincinnati groups.* 
The above quoted descriptions give the sum of the generic 
characters said to be possessed by twenty-six species and va- 
rieties, the majority of which are from the middle beds of the 
Cincinnati group of the Ohio valley. Under his description of 
Dekayella Mr. Ulrich, as we have seen, summed up the dif- 
ferential characters of his three genera. Dekayella is said to 
have comparatively thick walls in the mature region and 
to have numerous mesopores and two sets of acantho- 
pores, the larger set being sometimes present in the axial 
region. Dekayia has thin walls, few or no mesopores, and on- 
ly the large set of acanthopores. Heterotrypa has a frondes- 
cent type of growth and only the small set of acanthopores. 
* Bull. U.S. G. S., No. 173, 1900, pp. 226-228. 
