210 The American Geologist. April, 1902. 
above description, the figures and description of Edwards and 
Haime must decide for us the question of the type of Chaetetes 
frondosus. 
For the form now known as Heterotrypa frondosa (= 
Monticulipora mammulata Nicholson) I propose the name, 
used above, Dekayia perfrondosa.* 
The characters ascribed by Nicholson to Dekayia perfron- 
dosa are briefly as follows: 
Zoarium consisting of thin undulating expansions composed of two 
layers of corallites which diverge from an imaginary axis. Surface 
covered with rounded, conical, or elongated monticules which may be 
but slightly raised or may be conspicuously elevated above the sur- 
face. The monticules are composed of cells slightly larger (?) or 
certainly at times smaller than the average. Those on the sides of 
the monticules may be full sized while those at the apices are smaller. 
The distance between the monticules is from one-half line to one line 
(1 to2mm.). The cells are large and small, the latter always angular 
and varying in number. from almost none to moderately but not ex- 
cessively numerous. The larger have a diameter of from I-100 to I-50 
inch. The walls of the corallites are apparently amalgamated and 
thickened as they approach the surface. A variable, but often consid- 
erable number of spiniform tubuli (acanthopores) is always present. 
Large tubes with comparatively few and remote tabule which are 
always complete and horizontal. Tabula more numerous in the small 
tubes. ’ 
There are two particulars, especially important to the pres- 
ent discussion, in which the above description of this common 
and highly variable species should be amended. Dekayia per- 
frondosa sometimes has very numerous mesopores, and in 
some cases large as well as small acanthopores. I have also 
detected an occasional cystiphragm in some specimens. 
Figs. 15 and 16, Pl. LX, represent the ordinary appearance 
of tangential sections of D. perfrondosa. In these sections 
mesopores and acanthopores are relatively few, and none of 
the latter are of large size. The structure of the wall is charac- 
teristic of the group. (cf. also Callopora.) Each zocecium is 
* The pretix per is used in the intensive sense. D. perfiondosa is a character- 
istically frondescent form. 
The use of Dekayia as the name of the combined genera Dekayia E. & H., 
Dekayella Uir. and Heterotrypa Nicholson, is strictly in recognition of the 
priority of the former name. Personally I should much prefer the far more 
adequately defined and appropriate term Heterotrypa of Nicholson. That 
Dekayia aspera E, & H. is properly a member of this group there can be no 
doubt. As has been shown it has the two sets of acanthopores. It also has 
the peculiar wall structure described later in connection with D. perfrondosa 
(ef, figs. 10 and 15, pl. ix; figs 10 and 4, pl. x.) Its close relation to the latter 
form and to D, subfrondosa will be further pointed out in a later paragraph. 
