40 
MARINE FAUNA OF ST. ANDREWS. 
Subkingdom MOLLUSCA. 
Section I. MOLLUSC01 DA. 
Class I. POLYZOA. 
The majority of the Polyzoa come from the deep water or 
the bay; and, indeed, there are comparatively few to be met 
with between tide-marks that do not also occur in the former. 
The minute animals of the calcareous masses so characteristic 
of many of this group, perform none of those alterations on 
the surface of the earth which the equally tiny coral-polyps 
daily effect; yet their workmanship in our northern waters is 
as regular and beautiful as that fashioned by the latter in the 
tropical seas. The patterns of the Lepralice , for instance, 
excite admiration; and though the apparent resemblance in 
growth, superficial aspect, and position may suggest to some 
an analogy between them and the lichens of our rocks 
and trees, yet it is remote and unable to bear close criti¬ 
cism. It is true it is difficult to assign an exact function to 
these organisms ; but in some cases the calcareous crust of 
the Lepralice affords a better hold to many stationary marine 
animals than the rock itself. Moreover, after heavy-coated 
forms (like the Balani ) have reared themselves on this basis, 
it frequently happens that the original crust is loosened from 
its attachment, and both fall off together. The coating of 
Lepralice , also, may prevent to some extent the disintegration 
of soft rocks and stones. By removing a portion of bark with 
an adherent Balanus from a submerged thorn-tree, and care¬ 
fully detaching the former, a fine network of Lepralia is found 
lowest, then the calcareous coating of the Balanus ; and if 
the latter has perished, a rough layer of Cellepora pumicosa 
obliterates all trace of it from without. 
The Cheilostomatous Polyzoa are fairly represented; and 
several, e. g. Flustra and Gemellaria , occur in vast quantities 
attached to stones, shells, and corallines on the West Sands 
after storms. The majority are common to the eastern shores, 
