Mytilacea 
2. A superfamily or suborder of bivalves, com- 
prising the families Myttiida;, Avictilidce, 1'ra- 
xinidw, and those differentiated from them, 
raytilacean (mit-i-la'se-an), a. and n. I, . 
Mussel-like; mytiloid or" mytiliform; pertain- 
ing to the Mytilacea. 
II. n. A mussel or somo similar shell ; any 
member of the Mytilacea. 
mytilaceous (mit-i-la'shius), a. [< NL. Mi/tilim 
+ -aceous.] Resembling a mussel ; mytiliform ; 
mytiloid ; of or pertaining to the Mytilacea. 
Mytilaspis (mit-i-las'pis), n. [NL. (Targioni- 
Tozzetti, 1868), < Gr. [tvritof, a sea-mussel, + 
aoirlc, a round shield.] A large and important 
genus of scale-insects, of the homopterous 
family Coccidce and subfamily Diaspinte. They 
belong among the armored scales,* and have the scale 
long, narrow, more or less curved, with the exuvise at the 
anterior extremity. The genus is cosmopolitan, as are 
many of its species. M. pomarwm is the common oyster- 
shell scale-insect of the apple. Some discussion has arisen 
respecting the precedenceof this genus or Lepidosaphes of 
Shimer, proposed in January, 1868, but most systematists 
retain Mytuaspis as the generic name. See cut under 
scale-insect. 
Mytilidae (mi-til'i-de), . pi. [NL. (Fleming, 
1828), < Mytilus + -idee.'] A family of byssif- 
erous (byssogenous) asiphonate bivalve mol- 
lusks, typified by the genus Mytilus; the mus- 
sels. The shell is equivalve, inequilateral, thickly coated 
with epidermis, with a weak and generally toothless hinge 
and marginal ligament. The animal is dimyarian, with a 
large posterior and a small anterior muscle ; the mantle 
is united by its margins behind into a fringed rudiment 
of an anal siphon. A well-developed byssus is always 
present The species are mostly marine. Mytilus, Modi- 
olus t and Lithodomus are representative genera. These 
and their allies constitute the subfamily Mytilintf. See 
cuts under Mytilus, Modiola, Dreissenidce, and date-shell. 
mytiliform (ml-til'l-form), a. [< L. mytilus (see 
Mytilus), a mussel, + forma, form.] Shaped like 
a mussel-shell ; resembling a mussel ; mytiloid. 
MytiliiicB (mit-i-li'ne), n. pi. [NL., < Mytilus 
+ -t<B.] A subfamily of J/;/ttK<te, represented 
by the genus Mytilus and closely related forms. 
mytilite (mit'i-l'lt), n. [< NL. Mytilus + -ite'*.] 
A fossil mussel-shell like, or supposed to be, a 
member of the genus Mytilus, or referred to an 
old genus Mytilites. 
mytiloid (mit'i-loid), a. and . [< L. mytilus 
(see Mytilus), a mussel, + Gr. fMuf, form.] I. 
a. Like a mussel ; mytiliform ; of or pertaining 
to the MytiUdas. 
II. TO. A member of the family Mytilidce; a, 
mussel. 
mytilotoxine (mit"i-lo-tok'sin), M. [< Gr. fivri- 
/lof, a sea-mussel, + Tof(uc6v), poison, + -f 2 .] 
A leucomaine (CpHj^NO^) found in the com- 
mon mussel. It is an active poison. 
Mytilus (rait'i-lus), n. [NL.,< L. mytilus, mitu- 
IHS, < Gr. fivrDiOf, /urvtof, a sea-mussel, < ptif, a 
shell-fish: see mouse and niche."] 
A genus of bivalves to which 
very different limits have been 
assigned. In modern systems it is 
the typical genus of MytUidce, character- 
ized by its terminal umbones. M . tiu- 
Ite is the commonest mussel, found on 
most coasts, adhering by the byssus in 
multitudes to rocks, submerged wood, 
etc. They are often used for food, 
sometimes cultivated, and used in large 
quantities for manure. Also written 
Mylillus, Mytulus. 
myxa (mik'sii), .: pi. myxce 
(-se). [NL., < Gr. ptofr, nostril, 
beak, also mucus: see mucus.'] 
In ornith., the terminal part of 
the under mandible of a bird, 
as far as the symphysis or gonys extends, cor- 
responding to the dertrum of the upper mandi- 
ble. [Little used.] 
myxedema (mik-se-de'ma), n. [< Gr. fii>^a, mu- 
cus, + E. edema."] 'A disease having the follow- 
ing characters : (i) An increase and degeneration of 
connective tissue over the body, so that it yields an ex- 
traordinary quantity of mucin, and hence an edematoid 
condition of the skin, which does not, however, pit on pres- 
sure. This is accompanied by dystrophy of epidermic 
structures and failure of dermal secretions ; anaesthesia, 
paresthesiac neuralgias, and digestive troubles also are 
complained of. (2) Muscular and mental sluggishness 
which may advance to extreme dementia; subnormal tem- 
perature in most cases, and high arterial tension in many. 
(3) Atrophy or other disease of the thyroid gland. The 
disease usually occurs in women over forty years of age 
but has been observed in men and children. Its course is 
chronic, lasting six years and upward, and progressive, with 
occasional halts and sometimes temporary improvement. 
myxedematous (mik-se-dem'a-tus), a. [< myxe- 
dema(t-) + -mix."] Pertaining to, of the nature 
of, or affected with myxedema. 
3926 
Myxine (mik-si'ue), . [< Gr. /iif, slimr, + 
-itie 2 .'] A genus of myzonts which have a very 
slimy body and attach themselves to fishes by 
means of their sucker-like mouth, typical of 
the family Myxinida;; the hags. See cut un- 
der Afljr 1 , 3. 
Myxinida (mik-sin'i-de), ji. pi. [NL., < Myxine 
+ -id(e.~\ A family of hyperotretous marsipo- 
branchs, cyclostomes, or myzonts, represented 
by the genus Myxine. (a) In Gill's ichthyological 
system, hags with six pairs of branchial sacs which open 
by ducts confluent with an inferior median canal discharg- 
ing by one aperture. These hags have an elongate eel-like 
form, and live in the colder waters of both the northern 
and the southern hemisphere. They are destructive to 
other fishes. Often when a fish is caught upon the line, 
they bore into the body and feed upon the flesh. They 
are known as hags, hagflshes, slime-eels, and suckers. (6) In 
Gunther's system, a family of cyclpstomatous fishes whose 
nasal duct penetrates the palate, including the Myacinidce 
proper and the Heptatremidx or BdeUogtomidos. 
myxinoid (mik'si-noid), a. and n. I. a. Per- 
taining to the Myxinida! or Myxinoidcu , or hav- 
ing their characters. 
II. n. A myzont () of the family Myxinida; 
or Myxinoida", or (6) of the order Myxinoidea. 
myxochondroma (mik^so-kon-dro'ma), n.; pi. 
myxocliondromata (-ma-ta). [NL., < Gr. /"''|a, 
mucus, + NL. cnondroma, q. v.] A tumor com- 
posed of mucous tissue mixed with cartilage; 
myxoma united with chondroma. 
myxofibroma (mik"so-fl-br6'ma), n.; pi. myxo- 
fibromata (-ma-ta). [NL., < Gr. /ivl-a, mucus, 
4- NL. fibroma, q. v.] A tumor composed of 
mucous mixed with connective tissue. 
Myxogastres (mik-so-gas'trez), TO. pi. [NL. 
(Fries), < Gr. /"'fa, mucus, + yaarlip, stomach.] 
Same as Myxomycetes. 
myxogastric (mik-so-gas'trik), a. [< NL. Myxo- 
r/astr-es + -ie.] Same as myxogastrous. 
myxogastrous (mik-so-gas'trus), . [< NL. 
Myjcogastr-es + -os.] Pertaining to the Myxo- 
gastres. 
myxolipoma (mik"6o-li-p6'ma), .; pi. myxoli- 
pomata (-ma-ta). fNL., < Gif. //tfa, mucus, + 
NL. lipoma,'q. v.] A tumor composed of mu- 
cous mixed with fatty tissue. 
myxoma (mik-so'ma), TO. ; pi. myxomata (-ma- 
ta). [NL., < Gr. //('fa, mucus, + -oma."] A tu- 
mor consisting of mucous tissue that is, 
a tissue with round, fusiform, or stellate cells 
in a transparent, semifluid, intercellular sub- 
stance containing a large amount of mucin. 
Also called collonema. 
myxomatous (mik-som'a-tus), a. [< myxoma(t-) 
T -ous. ] Pertaining to a myxoma ; affected with 
myxoma. 
Myxomycetaceae (mik-so-ml-se-ta'se-e), M. pi. 
[NL., < Myxomycetes + -acea!.~] Same as Myxo- 
mycetes. 
Myxomycetes (mik'so-mi-se'tez), n.pl. [NL., 
< Gr. ftvja, mucus, + fii'Kqc, pi. fivur/rcc, a mush- 
room, fungus.] A group of fungus-like organ- 
isms, the slime-molds or slime-fungi, belong- 
ing, according to the classification of De Bary, 
to the Mycetozoa, and numbering about 300 
species. They form slimy yellow, brown, or purple 
(never green) masses of motile protoplasm during the 
period of active growth, and are then destitute of cell- 
wall and nucleus. Under certain conditions they secrete 
a cellulose wall and pass into a resting state. This rest- 
ing state is brought about either by the absence of the 
requisite moisture, producing larger, somewhat irregular 
masses, the so-called sclerotium stage, or when the plas- 
modium seems to have concluded its vegetative period, 
the protoplasm then becoming heaped into a mass which 
breaks up internally into a large number of rounded bod- 
ies, the spores, each one of which is provided with a cell- 
wall. Under proper conditions these spores burst their 
walls and become motile nucleated masses of protoplasm 
(swarm-spores) which divide separately by simple fission. 
After a few days two or more of these swarm-spores coa- 
lesce and form new plasmodia, which differ only in size 
from the original. They occur on decaying logs, tan-bark, 
decaying mosses, etc. See Mycetozoa. 
myxomycetous (mik"so-mi-se'tus), a. [< NL. 
Myxomycetes + -ous."] Pertaining to the Myxo- 
mycetes. 
myxont (mik'son), n. [< L. myxon, myxo(n-), < 
Gr. //if ow, also /iff /vof, a smooth sea-fish, a kind 
of mullet, appar. < //if a, mucus : see mucus."] A 
mullet of the family Mugilidas. 
myxopod (mik'so-pod), . and a. [< NL. niyxo- 
pus (-pod-), < Gr. /ifcfa, mucus, + 7rot>f (TTOI?-) = 
E. foot.'] I, n. A protozoan animal possessing 
pseudopodia, as distinguished from a mttNl/i/u- 
pod, one which has cilia or fiagella; one of the 
Myxopoda. See cut under Protomyxa. 
II. a. Same as myxopodous. 
Myzostomum 
Myxopoda (mik-sop'o-da), n.pl. [NL.: see 
myxopod.'] Protozoans whose locomotive ap- 
pendages assume the form of pseudopodia: 
synonymous with Rliizopoda. Huxley. 
myxopodous (mik-sop'o-dus), a. Of or per- 
taining to the Myxopoda; possessing pseudo- 
podia. Also myxopod. 
myxosarcoma (mik"so-sar-k6'ma), . ; pi. myx- 
osarcomahi (-ma-ta). ' [NL., < Gr. //ifo, mucus, 
+ adpKu/ia, a fleshy excrescence : see sarcoma.'] 
A tumor composed of mucous and sarcomatous 
tissue. 
myxosarcomatous (mik // so-sar-kom'a-tus), a. 
[< myxosarcoma(t-) + -ous.] Pertaining to a 
myxosarcoma. 
Myxospongiae (mik-so-spon'ji-e), n.pl. [NL., 
< Gr. fii'^a, mucus, + onoyyid, a sponge: see 
sponge.'] A division of the Spongtda or Porifera, 
established for the reception of the genus Hali- 
sarca, consisting of certain gelatinous sponges. 
myxospore (mik'so-spor), 71. [< Gr. /jifa, mu- 
cus, + <7jro/x>f, seed.] In certain fungi, a spore 
produced in the midst of a gelatinous mass, 
without evident differentiation of ascus or ba- 
sidium as in aseospores or basidiospores. 
myxosporous (mik-so-spo'rus), a. [< myxo- 
spore + -ous."] Containing, producing, or re- 
sembling a myxospore. 
myxotheca (mik-so-the'ka), n. ; pi. myxothecw 
(-se). [NL., < Gr. pnffe, mucus, + ftfra?, a sheath.] 
The inferior unguicorn of a bird's bill, or horny 
sheath of the end of the lower mandible, corre- 
sponding to the dertrotltfca of the upper man- 
dible. 
Myzomela (mi-zom'e-la), n. [NL., < Gr. /jiv- 
(uv, mutter, + //f/lof, song.] The typical ge- 
nus of Myzomelinue, containing most of the spe- 
cies of the subfamily, nearly 30 in number. 
The bill is long and slender, and curved ; the tail is two 
thirds as long as the wing ; the coloration of the males 
is chiefly black and red, with or without yellow on the 
under parts, and that of the females is generally plain 
olive above. M. cardinalis is known as the cardinal 
honey-eater; M. sanc/uinoleata as the sanguineous or 
cocJvtneal creeper; the former inhabits New Hebrides, the 
latter Australia. 
Myzomelina (mi-zom-e-H'ne), n.pl. [NL., < 
Myzomela + -mat."] A subfamily of Melipha- 
the 
', typified by the genus Myzomela. 
myzomeline (mi-/.om'e-lin), a. Pertaining to 
the Myzomelina;, or having their characters. 
myzont (mi'zont), a. and TO. [< NL. myzon (in 
pi. Myzontes), < Gr. fii-^wv (/wfovr-), ppr. of fti>- 
&iv, suck.] I. a. Sucking or suctorial, as a 
lamprey or hag; of or pertaining to the Myzon- 
tcs; cyclostomous or marsipobranchiate, as a 
fish. 
II. . Any member of the Myzontes; a lam- 
prey or hag. 
Myzontes (ml-zon'tez), n.pl. [NL., pi. of my- 
zon: see myzont."] A class of vertebrates in 
which the skull is incompletely developed and 
there is no lower iaw. The brain is distinctly de- 
veloped. The heart is also well developed, and partitioned 
into an auricle and a ventricle. The gills have a pouch- 
like form. In the adult the mouth is circular and suc- 
torial. The Myzontes are the lampreys and hags, repre- 
senting two orders, Hyperoartia and Hyperotreta. Also 
called Cyclostomi, Marffipobranchii, and Monorhina. 
Myzostomida (mi-zo-stom'i-da), n.pl. [NL., 
< Myzostomum + -id'a."] An order of doubtful 
affinities, referred by some to the worms and 
by others approximated to the mites. It com- 
prises symmetrical animals provided with an external 
chitinous cuticle, five pairs of movable parapodia, each 
with a hook and supporting rod, and an alimentary canal 
wfthoral and anal apertures, through which latter the eggs 
are extruded. They are parasitic on and in crinoids. Also 
JHyzostomata. 
Myzostomidae (mi-zo-stom'i-de), . pi. [NL., 
< Myzostomum + -idtt.~] A family of Myzosto- 
mida with ramified alimentary canal, parapodia 
connected by muscles which converge to a cen- 
tral muscular mass, body-cavity divided into 
paired chambers by incomplete septa, and usu- 
ally four pairs of suckers. They are hermaphrodite 
or dioecious ; the ova are evacuated through a cloaca ; and 
the male generative apertures are situated laterally. 
myzostomous (mi-zos'to-mus), a. Of or per- 
taining to the Myzostomida or having their 
characters. 
Myzostomum (ml-zos'to-mum), n. [NL., < Gr. 
uv&tv, suck, + oTo)/a, the mouth.] The typical 
genus of Myzostomidw, comprehending certain 
small creatures which are parasitic upon cri- 
noids. They are not over one fifth of an inch in length, 
and have the form of a flattened disk. Sitlxild, 1843, after 
Myiostoma of Leuckart, 1827. 
