POLYPI. 
658 
granules, that it dries entire on the axis, and retains its colours, which are often very bright and beautiful ; but it 
is soluble in acids. The Polypi of several species have been examined, and found to have eight toothed tenta- 
cula, and a stomach and other viscera, like those of Corollium. 
Among them, M. Lamouroux distinguishes Plexaures, which have the covering membrane thick, with the cells 
not prominent, and it effervesces but slightly with acids ; Ermicen, which have the same back, but the cells of 
the polypi prominent ; Murisen, which have the covering of moderate thickness, with projecting mammillae covered 
with rough and imbricated scales ; and Primnoa, in which the mamillae become imbricated by the one hanging 
partially over the other. 
Lithophyta,— 
The second tribe, have a fixed internal axis of stony consistency. The leading genera are, Isis, 
Madrepora, and Millipora ; but they admit of subdivision. 
Isis, have the axis branched, and no cells or cavities on its surface ; and the internal tunic of gelatinous matter 
is mixed with calcareous particles, as in Gorgonia. 
CoralUna [Isis nobilis of Linnaeus], is the Coral of commerce, so much admired for its fine red colour, and the 
high polish of which it is susceptible, and so often made into trinkets. There are very profitable fishings (or 
divings) for it in different parts of the Mediterranean. The covering is of a reddish colour, and contains cal- 
careous matter. The polypi have eight toothed arms, or tentacula. Melita, has the stony axis interrupted by 
nodes full of a substance of the consistency of cork. Isis, properly so called, has the horny part knotty ; and 
the bark thick, soft, and easily removed after death. Mopsia, has the bark much thinner, but also stronger. 
Madrepora (the Madrepores), — 
Have their stony substance sometimes branched, and sometimes in rounded masses, or in leaves ; but 
it is always furnished with laminae, concentrated toward points in the form of stars, or terminating in 
lines more or less serpentine. During life the stony part is enveloped in a horny bark, which is soft 
and gelatinous, and roughened by rosettes of tentacula, which are the Polypi, or rather the Actiniae, for 
they have more than one row of tentacula. The laminae of the polypi have some slight resemblance 
to those on the stony case ; and the covering and polypi contract a little upon being touched. 
The varieties of their general form, and the figures which are produced by the combinations of their laminae, 
have been made the foundation of numerous subdivisions ; but several of these run into others, so that they are 
not absolutely specific, and it will be impossible to fix them definitely until the relations between their forms 
and the polypi are known. 
When there is only a single star, circular or elongated, with many laminae, they are the Fimgia of Lamarck ; 
and their polype resembles a single Actinea, with numerous tentacula ; and the opening of the mouth corresponds 
exactly with the point toward which the lamin® converge. 
There are found among fossils stony polypidoms consisting of a single star, which appears never to have 
adhered to others. These are the Turbinata and Cyclolithus of Lamarck, and the Turbinolopsis, Lamouroux. 
When the Madrepore is branched, and the stars are confined to the extremities of each branch, it is the Caryo- 
pliyllia of Lamouroux. The branches are striated, and each star answers to a mouth surrounded by many 
tentacula. 
Oculina, have the small lateral branches very short, which gives them the appearance of having stars along the 
branches, as well as on the extremities, Madrepora, or Madrepores properly so called, have the whole surface 
roughened by little stars. Pocillopora, have little stars with pores in the intervals ; and Serialopora, have their 
stars in lines. Astrea, have a broad and generally convex surface, hollowed by crowded stars, each having a 
polype with numerous tentacula in a single row, in the centre of which is the mouth. Explanaria, are broad, 
with the stars on one side. Porites, has the stony substance branched. Meandrina, have the surface formed into 
little hills and valleys. In each valley there are mouths ; but the tentacula, instead of forming stars or rosettes 
around them, are ranged along the sides of the valley. In some, however, the mouths are merely festooned. If 
the hills which separate the valleys are raised into crests furrowed on both sides, they are called Pavonia ; and 
mouths, usually without tentacula, are found in the valleys, the crests probably acting as substitutes for the latter. 
There are also others, which have these hills conical or star-shaped, and the principal distinction of them is 
having the polypi on the projecting parts or in the hollows. Agaricina, are composed of laminae, having valleys 
only on the one side, and the sides of the valleys furrowed. It is probable that we should consider as nearly 
allied to the Madrepores, certain polypidoms composed of cylinders, the sections of which form stars. These are 
Sarcinula, and when they have a solid axis, they are perhaps nearly allied to Tubipora, in the first family of the 
order. 
Millipora, — 
Which compose the third genus, have the stony portion much diversified in shape, and the surface 
scooped only into small holes or pores, and sometimes there are no apparent perforations. Disticho- 
pora, have strongly marked pores on two sides of the branches. Millipora proper, are solid and 
variously branched. Sometimes the pores are not discernible, and they are Nullipores. Eschora, have 
flattened and leaf-like expansions. Retepora, are Eschorse pierced like a net-work. Adeom, are 
Eschorse on articulated stems, entire, or pierced like a net-work. 
