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FAMILY II.— ZOANTHIDM:. 
TJie polypes in this family are persistently fixed, and 
aggregated : the adherent base extending itself laterally, 
and sending up new polypes at intervals, which remain 
permanently united to eaeh other, and to the primary 
polype. The extension may he in irregular lines, earrying 
the polypes in single file; in broad bands, supporting several 
abreast ; or in all directions, producing large clustered 
masses, incrusting the foreign body to which they happen 
to be adherent. 
This variation in the manner of base-extension has been 
hitherto considered as so important, that genera have been 
constituted on this character alone, — Zoantlius, including 
those whose base runs in lines ; PahjtJwa, such as form 
carpet- like surfaces. But evidence will presently be 
adduced to show that these variations may occur in the 
same species. Again, the genera Mammilifera and Corti- 
cifera, of Lesueur, have been formed for clustered species ; 
the former being fleshy, with a raucous sm’face, not en- 
veloped in sand ; the latter “ inclosed in cellules of sand, 
agglutinated ; the cellules themselves agglutinated for their 
whole length, and forming a corticiferous expansion.” It 
appears, however, from Lesueur’s own description, that 
what he considered “ cellules,” inhabited by the animals, 
was simply the integument of each polype, in which sand 
was imbedded. The presence or absence of sand, however, 
can in no wise be allowed to constitute a generic distinc- 
tion. I cannot, therefore, recognise in the family more 
than the single genus, Zoanthus. 
