This species is related to P. emarginata, from which it may be distinguished by the following characters:— zoarium.
The zoarium is of delicate appearance and branches sparingly.
The zoarium consists of a circular or oval mass of no great size.
Major Walton found it growing over a zoarium of Hislopia lacustris.
The arrangement of the polypides in the zoarium and the general structure of the statoblasts are very similar in the two species.
A zoarium with its included polypides is finally produced from the young polypide by the rapid development of buds.
It possesses a creeping "sole" or organ of progression at the base of the zoarium.
The zoœcia are not distinct from one another, but in dendritic forms the zoarium is divided irregularly by chitinous partitions.
The zoarium consists primarily of a main axis running in a straight line, with lateral branches that point forwards and outwards.
The zoarium as a whole is either recumbent and adherent or at least partly vertical.