CONCHOLOGY, 
50 
vjfib'e th ere. This creature is wonderfully minute when 
newly excluded from the egg; but it grows to the length 
of four or fix inches, and .fometimes more. When the 
bottom cf a vefiel,'or any piece of wood which is con- 
ftantly under water, is inhabited by thefe worms, it is full 
of (mall holes; but no damage appears till the outer parts 
are cutaway : then their (belly habitations come into view ; 
in which there is a large (pace for incloling the animal, and 
furrounding it with water. There is an evident care in 
thefe creatures never to injure one another’s habitations ; 
by this, means each cafe or (hell is preferved entire ; and 
in (uch pieces of wood as have been found eaten by them 
into a fort of honeycomb, there never is feen a padage or 
communication between any two of the (hells, though the 
woody matter between them often is not thicker than a 
piece of writing-paper. They penetrate fome kinds of 
wood much more eafily than others. They make their 
way molt quickly into fir and alder, and there grow to 
the greateft fize. In the oak they make lefs progrefs, and 
appear final! and feeble, and their (hells are much difco- 
loured. Since each of thefe animals is lodged in a foli- 
tary cell, and has no accefs to thofe of its own fpecies, it 
has been matter of furprife bow’ they (liould increafe tofo 
vaft a multitude. Upon diffe&ing them, it appears that 
every individual has the parts of both fexes, and is there¬ 
fore fuppofed to propagate by itfelf. Thefe fea-w'onns 
appear to have the fame office allotted them in the wa¬ 
ters, which the termites have on the land. They will 
appear, on a very little confideration, notvvithftanding 
they are fo pernicious to (hipping, to be molt important 
beings in the great chain of creation, arid pleafingly de- 
monftrate that infinitely wife and gracious Power which 
formed, and (till preferves, the wdiole in 1’uch wonderful 
order and beauty ; for, if it was not for the rapacity of 
thefe and fuch animals, tropical rivers, and, indeed, the 
ocean itfelf, would be choked with the bodies of trees 
which are annually carried down by the rapid torrents, 
as many of them would laft for ages, and probably be pro¬ 
ductive of evils, of which, happily, we cannot in the pre- 
fent harmonious ltate of things form any idea; whereas 
now, being confirmed by thefe animals, they are more 
eafily broken in pieces by the waves; and the fragments 
which are not devoured become fpecifically lighter, and 
are confequently more readily and more effedually thrown 
on (bore, where the fun, wind, infefts, and various other 
inlhuments, (peedily promote their entire diffiolution. 
The Sabella is a (imiiar creature, the (hell of which 
is tubulous, and formed of grains of fand cemented to¬ 
gether and hardened into a cruftaceous covering, by the 
mucous matter which iflfues from the included inhabitant. 
There are twenty-five fpecies, of various (izes, from half 
an inch to nine inches long. Some of them inhabit the 
Britifti feas, the coafts of Norway and Greenland, and the 
Cape of Good Hope ; others, of the larger fize, are found 
in the Indian ocean, and in the South Sea ; on the coafts 
of America, and in the (alt lakes of Thuringia. 
Gualtieri ranks the famous (hell the wentletrap, orftair- 
caTe, with vermiculi: he gives for reafon, that the ipires 
of this (hell are mere loole ones, not produced from, or 
anyway connefiled orfupported by, a pillar 01; columella, 
running through the middle of the (hell its whole length, 
as is the conltant and true llrufture of all turbinated 
ill ells. Davila places it among his vermiculares, without 
giving any realon for fo doing. There are alfo vermiculi 
which have concamerations, or are divided into chambers 
by a few or many tranfverfe plates running acrofs the 
tube; but they are (eldorn regular, or let at equididant 
intervals, and are not pierced by a pipe or iiphunculus, 
that communicates from chamber to chamber, fo as to 
permit the filh to penetrate more than one chamber or 
inclofure at a time, in which particulars they eflentially 
differ from the concamerated (hells. JBefides, thefe con¬ 
camerations do not fieem conftant to any particular fpe¬ 
cies, and appear rather the clofing up, and deferting the 
old place of habitation of the fiffi, when it augments its 
(hell; juft like the bottom fplree of a turbinated (hell, 
which the animal fills up as it grows bigger, and enlarges 
it habitation.' The vermiculi are frequently found in 
the foffil (late; but we do not.recolleft any fpecies, but 
what is known in a living (late recent from the fea. 
DENTALIA, or. TUSK-LIKE SHELLS. 
This family of fimple (hells is likewife of the terebelia 
or piercer fpecies; but is l'eparated from the preceding 
genera, on account of the difference in its conformation. 
The effential chara&er of this (hell is, that it is fimple, 
tubular; of a regular, determinate, curved, conical, (hape; 
and open at both ends. This (hell is found from one to 
four or five inches long. There are twenty-one fpecies, 
which are natives of the Indian ocean, the Mediterra¬ 
nean fea, the Engliffi channel, and moll of the fea coafts 
in different parts of the world. 
The Conchology-Plate I. exhibits different figures of 
the vermiculi, or fea-worm (hells. Fig. i. Aclufterofthe 
ferpula contortupiicata, from Knorr. Fig. 2. The large 
green-furrowed dentale of the Eaft Indies. Fig. 3. The 
linooth yeilowifh dentale of the Engliffi fea. 
The PATELLA, or LIMPET. 
This family derives its generic name from its refem- 
blance to a little plate 5 like this utenfil, the limpets are 
for the mod part round, or oval, or approaching thereto; 
the part that contains the fiffi is concave, fmooth, and 
often finely waflied with colours. The (hell is more or 
lefs conical; it has no contour, but the rock or other 
hard body to which it adheres, (erves as a kind of fecund, 
or under (hell, to preferve it from injury. On this ac¬ 
count Aids ovandus and Rondeletius chided the limpets 
among the bivalves ; but in this error they have not been 
followed by any other writer. The apex, or eye of the 
limpet, is either wdiole or perforated, and is feldom placed 
exadlly in the middle of the (hell, but mod commonly in¬ 
clines towards one end; that is, taking it in its longed: 
dimenfions. The rim of the (hell, which forms its bate, 
is likewife various, fometimes without any prominencies 
or fmooth, fometimes with large ones or jagged, and 
fometimes with ftits only, or crenated. Their external 
furface is often rough and fcabrous, and their, apices of¬ 
ten imperfect; for, mod of this family adhering to the 
rocks, they are much expofed to the fun during ebb, and 
to all the violences that render dead (hells unacceptable 
to the curious. Though it commonly happens, that the 
(hells moll remarkable for the brilliancy of their colours 
are of the fimpled form, as the nerits, olives, volutes, See. 
yet this tribe feems an exception. It is true there are 
confiderable numbers that have very lively colours; yet, 
in general, they abound with lefs.variety than mod other 
(hells. In fome parts of England the limpets have ob¬ 
tained the name of nipple-jhells \ becaute its convexity ter¬ 
minates in a kind of papilla near the center. 
The limpets are very numerous, confiding of no lefs 
than 238 fpecies, which Da Coda divides into three ge¬ 
nera of (hells, viz. 1. Whole or entire limpets, (patella 
vertice Integra,) or that are not perforated or open at the 
top. 2. Chambered limpets, (patella concamerata five 
cavitate Jlylo biterno donata.) 3. Pierced or perforated 
limpets or ma(ks, (patella vertice perforata,) that have 
their tops perforated with a.hoie pierced quite through 
the fliell. The firft genus, or whole limpet, is very nume¬ 
rous. The lecond, or chambered limpet, has many fpe¬ 
cies : but the third genus, or perforated limpet, or mafks, 
has but few fpecies. Europe, however, affords blit very few. 
The fined, and lagged are from the Eaft Indies and Africa, 
efpecially from the Cape of Good Hope. America has 
many of the chambered and fmaller kinds : and late dif- 
coveries have brought fome large and fine limpets from 
the Streights of Magellan and the South Sea. 
Thefe are all the notices that occur relative to the re¬ 
cent limpets, or thofe known from fea. But there are 
many foffil (hells which are not yet difeovered or known 
in 
