M A C 
blow ; from the flowing of the blood, and the length of 
time it happened to live after the fall, &c. 
MACTATOR,/, [Latin.] One that kills for facri- 
fice; a murderer. 
MAC'TRA,/. the Pellucid Oyster ; in helmintho¬ 
logy, a genus of teltaceous worms. Generic characters— 
Animal a tethys; (hell bivalve, unequal-fided, equivalve; 
middle tooth of the hinge complicated, with a fmall hol¬ 
low on each fide, lateral ones remote, and infested into 
each other. There are twenty-feven fpecies, inhabiting 
the coafts of all quarters of the world ; and four of them 
are found on our own coafts. They are of different fizes, 
from that of a man’s hand, downwards, fo that fome of 
them are fcarcely an inch broad. The (hells are like wife 
exceedingly different, fome being fmooth, others wrinkled; 
fome are wedge-fliaped, others ovate; they are alfo dia¬ 
phanous, pellucid, and femitran(parent; fome are ltriate, 
banded, white, or fawn-coloured. 
1. Madtra Spengleri t (hell fmooth, with a flat anterior 
margin, on which is a lunate gape. It is found at the 
Cape of Good Hope, nearly as large as a man’s hand, and 
is a little gaping, pale, fub-diaphanous, fun-triangular. 
The gape, before the hinge, is lunate, acute, and reach¬ 
ing to the hollow of the hinge ; the beaks are incurved, 
and the teeth of the hinge triangular. 
a. Madtra plicatoria; (hell with tranfverfe wrinkled 
plaits, diaphonous-; the anterior margin is flattilh ; behind 
the beaks is a cotnpreffed oblong gape. It is found in the 
Indian ocean, and is from one to two inches long, and 
two inches and a half broad. The (hell of this fpecies is 
as thin as paper, with fmooth lanceolate depreftions on 
each fide the hinge ; the anterior one flattilh, with a ridge 
near the beaks; the polierior impreffed, and more ovate; 
beaks incurved ; lateral teeth of the hinge coinpofed of 
two parallel membranes. 
3. Madtra papyracea : fliell very thin, pellucid, and 
white; it is convex, the fore-part a little gaping, very 
finely ltriate, and ribbed. It is found in the Nicobar 
iflands, but is extremely rare ; it refembles the lalt, but is 
more convex and unequal-fided ; except in the hinge, it 
is very like a tellina. 
4. Madtra ftriatula : (hell fmooth and diaphanous; beaks 
fubftriate, with a fmooth marginal imprelfion before them, 
furrounded with a rim. It inhabits the Coromandel coalt, 
and is found alfo in the Mediterranean; is about two 
inches and a half long, and three inches broad ; it is white, 
fub-triangular, rather convex, a little gaping on the fore- 
margin. 
5. Madtra ftriata: (hell thick and triangular, with 
ftrong, thick, crowded, fmooth, arched ftria ; it is white, 
and glabrous within at the beaks. Is found in the Medi¬ 
terranean ; and is about the fize of the laft. 
6. Madtra glabrata: (hell fmooth, diaphanous,and ftriate; 
beaks very fmooth, the margins on each fide ftriate. It is 
found in the African and Indian oceans; and is about 
the fize of the ltriata; colour white. 
7. Madtra rotundata : (hell obtulely triangular, whiti(h, 
with milk-white bands on the beaks ; the margins, on each 
fide the beaks, violet. Inhabits the Mediterranean ; fize 
of the laft. 
8. Madtra nitida: (hell fnowy and diaphanous; the de¬ 
preftions on each fide the beaks are ftriate ; the anterior 
ones marked with a ridge. The (hell is triangular, and 
the beaks retroverted and diftant. 
9. Madtra corallina t (hell fmooth, fub-diaphanous,and 
white, with paler bands ; it is about two inches broad, 
and an inch and a half long, triangular, with obtufe de¬ 
preftions on each fide the beaks. Inhabits the Mediter¬ 
ranean and Guinea feas. 
10. Madtra ladtea: fliell thin, pellucid, white; the fore¬ 
part very finely ftriate, with paler bands. It is found in 
the Indian ocean : it refembles the laft, but is thinner, 
and more convex; the anterior part is flattilh, with an 
obtufe margin. 
u. Madtra ftultorum; (hell femi-tranfparent, fmooth, 
M A C 53 
and gtoffy; it is- obfoletely radiate, white without, a»4 
purplifh within. This is found on the fliores of our own 
country, and alfo in the American feas-; and is only the 
fize of a hazel-nut. 
12. Madtra grandis: (hell femi-tranfparent, fmooth, 
fawn-colour, with pale rays; the beak and hinge placed 
below the middle. This is very like the lalt ; is more 
than three inches long, and two broad, gaping at the ex¬ 
treme angle ; the anterior fide more produced. 
13. 'Madtra folkia : (hell opaque and fmoothifli, thick 
and ftrong;'colour white, to a yellowilh-brown, frequently 
marked with blue or pale orange belts. While alive it is 
fmooth, and when dead it has a few high tranfverfe Arise, 
like ribs; the lateral teeth are fmall, elongated with a large 
hollow ; the middle tooth is lmall. Found on the (hores 
of Europe. 
14. Madtra lutrarra : (hell oval-oblong and fmooth, 
without lateral teeth. This-inhabits the European coafts, 
near the mouths of rivers; it refembles a mya gaping,at 
both ends ; in colour it is of a dirty white, or yellowifh 
tinged with orange, and irregularly clouded with brown ; 
hinge with a fmall and large triangular cavity in one 
valve, and a fimilar cavity with an elevated triangular 
tooth in the other. 
15. Madtra cygnus: (hell fnowy, thick, and three-fided, 
very finely ftriate tranfverfely; the fore-partis flattilh, 
and flightiy wrinkled ; behind the beaks a broad, heart- 
(haped, thinly-ftriate, imprellion. Found on the coafts of 
Tranquebar; an inch long, and rather more than an inch 
broad. 
16. Madtra maculatat (hell obtufely triangular, fmooth, 
thin, with pellucid chefnut fpots; within white, and very 
finely ftriate. 
17. Madtra turgida : (hell inflated, faintly ftriate, of an 
ochre colour, but white within ; the beaks diftant, pur- 
plilh ; the hinge has a fupernumerary triangular double 
tooth. It inhabits Tranquebar, and is nearly three inches 
long, and more than that broad ; it is thin, pellucid, finely 
ftriate, and wrinkled before and behind. 
18. Mattra violacea : (hell thin, obfoletely radiate, finely 
ftriate tranfverfely ; margins on each fide the beaks whitifh j 
hinge with a fupernumerary double triangular tooth. This 
is found on the coalts of Tranquebar, and is about two 
inches long, and three broad. The (hell is brittle, gaping 
here and there, the anterior margin oblong, elevated, and 
wrinkled. 
19. Madtra cuneata: (hell wedge-fhaped, blue, finely 
ftriate tranfverfely ; the margin crenuiate within. It re¬ 
fembles in many relpeclsthe laft, but is only an inch long, 
and not fo much as that broad ; it is fometimes white. 
so. Madtra glauca: (hell ovate, dirty white, with glau¬ 
cous rays, very finely ftriate tranfverfely; the anterior 
part wrinkled. It inhabits the Mediterranean ; the fame 
fize as the turgida: the beaks are turned backwards, with 
a narrow gape between them. 
21. Mactra pellucida : (hell ovate, thin, and of a pel- 
lucid white, with unequal tranfverfe ftrise. It inhabits 
Guinea; is one inch and a quarter long, and about two 
broad ; the (hell is brittle, a little produced forwards, and 
gaping. 
22. Madtra fragilis: (hell ovate, thin, fmooth, pellucid ; 
flattifli; the anterior gape tranfverfely ftriate, and wrinkled. 
It inhabits the Nicobar- iflands, and refembles the laft. 
The (hell is gaping, and flightiy plaited on the fore-part; 
the margin is acute, fubangular before and rounded be¬ 
hind. 
2.3. Madtra rugofa: (hell ovate, dirty white, with ele¬ 
vated longitudinal ftriae crofting the tranfverfe ones, which 
are a little more railed. It is thick and white within j 
about two inches and a half long, and the fame in breadth. 
24^ Madtra Nicobarica : (hell ovate, thin, and pellucid 
on the fore-part; the hind-part with cancellate (trite. 
Found in and about the Nicobar iflands. 
25. Madtra complanata: lhell ovate, thin, with arched 
plaits, tranfverfely ftriate. It inhabits India, and is of a 
3 bluifh 
