$88 M O N O 
brown • the flxell is very convex, rounded in front, and 
lunated behind, where it joins the lower part of the body : 
this, which is of the fame cruftaceous nature, is marked 
on each fide into feveral fpiny incilions. The legs, which 
are fevcn on each fide, are fituated beneath the concavity 
of the large or rounded part of the fhell, and are each ter¬ 
minated by a double claw, thofe of the lowed; pair having 
fome additional precedes : the branchiae, or refpiratory 
organs, are difpofed in the form of feveral flat, rounded, 
imbricated, lamellie, on each fide the lower part of the 
body : the tail, which is ftraight, triangular, and of the 
fame cruftaceous nature with the reft of the fhell, is equal 
in length to the whole body, and gradually tapers to a 
fharp point. The eyes in this l'pecies, intlead of being 
approximated, as required in the Linnasan generic cha¬ 
racter, are extremely diftant from each other, being fitu¬ 
ated towards the tides of the fhell: they are of a femilunar 
form, and the furface is divided into a great number of 
minute conical convexities : this part however fliould be 
confidered only as conftituting the cornea, or exterior co¬ 
vering of each eye; the organs themfelves being, accord¬ 
ing to the obfervations of Mr. Petiver, in the Philofophical 
TranfaCtions, placed on a pedicle beneath each of the 
above-mentioned femilunar cornea;. Petiver’s words are 
thefe : “ The whole ftruCture of this animal is very re¬ 
markable, and particularly his eyes ; viz. between the 
fourth and laft pair of claws on each fide, reckoning from 
his mouth, and excluding the linall pair there placed, are 
inferted the rudiments of another pair, or a claw broken 
off on each fide at the fecond joint or elbow ; on thefe ex¬ 
tremities are the eyes, like thofe of the horns of fnails ; 
but under the cover of a thick and opake fhell, Nature in 
that plac.e has wonderfully contrived a tranfparent lan¬ 
tern, through which the light is conveyed.” A reduced 
view of this monftrous in left is given at fig. 3. and, as ly¬ 
ing on its back, at fig. 4. 
56. Monoculus cyclops: fhell convex, with three lines 
of raifed fpines ; tail very long, and unarmed. It is about 
one-third the fize of the polyphemus; and is found in 
India. 
57. Monoculus apus, the apodal monoculus : fhell ob¬ 
long, truncate, and ferrate behind; tail ending in two 
bridles. This is the largeli: of the European monoculi. 
It is a rare fpecies in this country, having been only ob- 
ferved in a few particular fituations in ftagnant water. In 
its general fliape it is confiderably allied to the large exo¬ 
tic fpecies above-deferibed, but the form of the body is 
more lengthened. The branchiae, or refpiratory organs, 
are large, and diftributed into numerous imbricated rows 
on the under part of the body ; beneath the front is a pair 
of jointed trifid arms, extending on each fide to a conii- 
derable diitance; the eyes are placed near each other in 
front of the fhell; the tail is terminated by a pair of long 
forks, or fetaceous proceffes ; the colour of the whole in- 
feifl is of a pale greenifh-brown above, and reddifh be¬ 
neath. An account has been given in the 40th vol. of the 
Phil. Tranf. that this fpecies has been feen in numbers in 
a pond at Bexley, in Kent. It is all'o added, that the fame 
pond, having been perfeftly dried, and being luddenly 
filled, during a heavy thunder-florm, fwarms of the fame 
animals were again obferved in it within the fpace of for¬ 
ty-eight hours after. This curious fpecies is fhovvn in 
three different pofitions, at fig. 5, 6, 7. 
58. Monoculus pifcinus: fhell heart-fhaped and flat; 
body fhort; tail bifid, and compofed of one thin flap. 
It is a native of European leas; found on flounders, cod- 
fifh, falmon, &c. adhering on the outfide between the 
f'cales, running fwiftly, with its tail elevated, both on the 
fiih and on the water. 
59. Monoculus pennigerus : fhell hemifpherical, with 
a linear future; tail feathered. Inhabits f re Hi water. 
60. Monoculus falmoneus : fhell oblong; tail imbri¬ 
cate, and four-leaved. It is found, as its name denotes, 
flicking to the falmon, between the feales. 
61. Monoculus nodtiiucus, the night-fhining monocu- 
C U L U S. 
lus. A few years ago, captain Horfhurg prefented fir 
Jofeph Banks with fome notes on the luminous appear¬ 
ance of the fea, and a drawing of a pholphorefeent ma¬ 
rine infedl, which have been pubiifhed in a paper of Mr. 
Macartney’s communicated to the Royal Society, in 18x0. 
Captain Horfburg remarks, that the luminous Hate of the 
fea between the tropics is generally accompanied with the 
appearance of a great number of marine animals, of va¬ 
rious kinds, upon the furface of the water; to many of 
which he does not, however, attribute the property of 
fhining. At other times, when the water which gave out 
light was examined, it appeared only to contain fmall 
particles of a duiky ltraw-colour, which difiblved under 
the flighted: touch of the finger. Captain Horfburg like- 
wife obferves, that in Bombay, during the hot weather in 
the months of May and June, he has frequently feen 
the edges of the fea much illuminated by minute fpark- 
ling points. Thefe, whilft in the water, always avoided 
feizure, by-moving away from the hand, fo that it was 
with difficulty he procured any of them. Upon two oc- 
cafions he fucceeded in detefling the animals that caufed 
the light of the fea. At fun-rife, on April 12th, 1798, 
in the Arabian Sea, he perceived feveral luminous fpots 
in the water, which conceiving to be animals, he went in 
the boat, and with fome difficulty caught one. This jli¬ 
fe 61 , he fays, refembied the wood-loufe in appearance, 
and was about one-third of an inqli in length. When 
viewed with the microfcope, it feemed to be formed by 
feftions of a thin cruftaceous nature. During the time 
any fluid remained in the animal, it flione brilliantly like 
the fire-fly. In the month of June of the fame year, he 
picked up an infedt on a fandy beach, which gave light. 
This was alfo covered with a thin fhell, but was of a dif¬ 
ferent fhape and a larger fize than the animal taken in 
the Arabian Sea. Mr. Macartney entertains no doubt 
that both thefe infefts were monoculi. The firft he refers 
to the divifion Limulus of Miiller, and gives it the fpe- 
cific name of nodtiiucus. Phil. Tranf. 1810. part ii. 
VIII. Lynceus; with the Jhells bivalve , eyes two, antennae 
capillary. 
62. Monoculus roftratus, the beaked monoculus: body 
ovate, cruftaceous, of a pale yellow colour, with a darker 
longitudinal line along each fide ; antennae four, the fu- 
perior pair bifid near the bale, one branch moderately 
long, the other very fnort; the lower pair Ample, and 
nearly as long as the body, the three firft joints large ; all 
thefe are hirfute, and incline downwards : eyes large, pe¬ 
dunculate, and reticulated, appearing in a ftrong light 
crimfon ; thefe are covered by a pointed beak or fhield a 
little incurvated, convex above, and concave beneath : 
legs three pairs, flightly bifid and very hirfute ; between 
thefe and the front are feveral fafciculi of briftles ; tail 
longer than the body, confiding of five joints elevated at 
their jundlion, the middle one furnilhed with two fmall 
appendages beneath : to the end of the tail are attached 
two tubulate caudal fins terminated by a long fetaceous 
appendage, and covered with hair. The extreme length, 
to the end of the tail, three eighths of an inch. When 
in motion, the fafciculi beneath, which appear to be ab¬ 
dominal fins, as well as the fuperior antennae, were ob¬ 
ferved to be in continual motion : the inferior antenna 
were ufually motionlefs, and brought under the body. 
This marine monoculus was difeovered on the fouth 
coaft of Devonlhire, by Mr. Montagu, F. L. S. and is de- 
feribed by him in the Linn. Tranf. vol. xi. He fuppofes 
it to be a new fpecies. It is fliown magnified at fig. 8. 
63. Monoculus lynceus, the luminous monoculus. In 
the year 1754, M. Godeheu de Riville difeovered alumi¬ 
nous teftaceous infeft on the coaft of Malabar, which ap¬ 
pears to belong to this divifion of the genus. Riville, 
perceiving the lea around his fhip to emit a very brilliant 
light, procured l'ome of the water and ftrained it; after 
which it ceafed to fliine, but the cloth was covered with 
luminous fpecks, that refembied in form and magnitude 
3 the 
