346 J. D. Dana on Zoophyies. 
over the surface between the disks; and the same is true of the 
Echinopore, or at least partly so, for the writer observed no ten- 
tacles in the two species he examined. e same reason shows 
that the moss-like subdivision of tentacles, observed in some Ac- 
tinide, is a character only of generic importance, for it takes place 
generally in such species as live more or less buried in the sand 
or mud, which fact seems to require an extension of the aera- 
ve been separated to form the group Madreporacea; but not- 
ithstanding this point of resemblance, the several genera are as 
closely related to species having a greater number of tentacles. 
The occurrence of suctorial vesicles on the lateral surface 0 
disk, is a character of only generic importance. : ‘ 
Color is seldom of much importance, even for trivial distine- 
tions. Yet the mode of arrangement of colors may be charac- 
teristic of species. A mutual dependence ‘or relation of certain 
colors may possibly be hereafter ascertained, by which a knowl- 
edge of one will determine the others that may be possible m 
a species; and in such a case, the character may have a value 
which cannot now be allowed it. ‘eta 
V. Secretion of Coral.—1. The secretion or non-secretion of 
coral internally, is at the best no more than a family distinction ; 
and among the Aleyonaria it is only generic. This is an admitted 
truth with regard to calcareous secretions among Molluscs ; and 
Olivi and Blainville long since acknowledged it with reference to 
zoophytes. : ‘ 
3. The nature of coral secretions sometimes affords generic 
distinctions, and with other characters, in some instances, distil- 
the surface. The Antipathi form only basal horny secretions, 
and therefore have a horny axis. The Aleyonaria are more Ll 
rious in this character, the different genera having their peculiar- 
