-th 
ent indicative of verbs, as in siiit/cth, hopfth, 
etc., or hath, doth, etc. It remains in archaic use, 
in poetical and scriptural language, the ordinary modern 
form being -, -es, as in tings, hopes, has, dues, etc. In 
Middle English and Anglo-Saxon use it was often con- 
tracted with a preceding radical d or ( into (, as fint for 
findeth, sit for siteth, sitttth, etc. 
tha 1 t, <i<li'- A Middle English variant of thti 1 . 
tha'-'t, pron. An obsolete form of the 1 and they 1 . 
thaar, . See thar 3 . 
thack 1 (thak), . An obsolete or dialectal 
(Scotch) form of thatch Under thack and rape, 
under thatch and rope : said of stacks in the barn-yard 
when they are thatched in for the winter, the thatch be- 
ing secured with straw ropes; hence, figuratively, snug 
and comfortable. [Scotch.] 
thack 1 (thak), v. An obsolete or dialectal 
(Scotch) form of thatch. 
thack 2 t (thak), v. t. [< ME. thal-kcn, < AS. thac- 
eian = Icel. thjokka, later also thjaka = Norw. 
tjaaka, strike, beat; cf. Icel. thykkr, a thump, 
blow. Cf. aucack and whack.] To strike; 
thump; thwack. Chaucer. 
thack 2 t, a. [< ME. thacce: see thacW, r.] A 
stroke ; a thwack. 
For when thacces of anguych watz hid in my sawle, 
Thenne I remembred me ryjt of my rych lorde, 
Prayande him for peW his prophete to here. 
Alliterative Poems (ed. Morris), iii. 325. 
thacker (thak'er), n. An obsolete or dialectal 
form of thatcher. 
thae (THa), pron. A Scotch form of tho%, obso- 
lete or dialectal plural of the 1 and that. 
thaff (thaf), n. Same as teff. 
thaht, conj. A Middle English form of though. 
thakket, . t. A Middle English form of thack 2 . 
thalamencephal(thal-a-inen'se-fal), M. [< thal- 
amencephalon.] Same as thalamencephalon. 
thalamencephalic (thal-a-men-se-fal'ik or 
-sef'a-lik), a. [< thalameiicephal + -ic.] Of or 
pertaining to the thalamencephalon ; dience- 
phalic. 
thalamencephalon (thaFa-men-sefa-lou), n. 
[NL., < Gr. 6aJM/x>c, an inner chamber, + e-yitt- 
0<zAof, the brain : see thalamus and encephalon.] 
The parts of the brain about the third ventricle 
developed from the hinder part of the first pri- 
mary cerebral vesicle, including the thalami, 
the optic tracts and chiasma, the infundibulum 
and cerebral part of the pituitary body, the 
corpora albicantia, the conarium, the ependy- 
mal part of the velum iiiterpositum, a lamina 
cinerea, and other structures. Also called di- 
encephahn, interbrain, 'tween-brain. See cuts 
under Elasmobranchii, encephalon, Rana, Petro- 
myzontidx, and cerebral. 
thalami, . Plural of thalamus. 
thalamia, n. Plural of thalamium. 
thalamic (tbal'a-mik), a. [< thalamus + -ic.] 
Of or pertaining to the optic thalamus Thal- 
amic commissure of the brain, the middle, soft, or gray 
commissure; the medicommissure. 
Thalamiflorae (thal"a-mi-fl6're), n. pi. [NL. : 
see thalamifloroiis.] A group of orders of poly- 
petalpus plants, constituting the first of three 
divisions called series by Beutham and Hooker. 
It is distinguished from the others, the Disci/torse and 
Calyciflaree, by the usual insertion of the petals, stamens, 
and pistils on the receptacle, not on a disk or on the calyx. 
In these orders the sepals are usually distinct, herbaceous, 
imbricate, or valvate, and free from the ovary ; and the 
receptacle is small and elevated or stalk-like. The group 
embraces the 6 cohorts Kanales, Parietales, Polygalinte, 
Caryophyttinm, Guttiferales, and Malvales, including 35 or- 
ders, in 20 of which the stamens are commonly numerous, 
in the others more often definite. 
thalamifloral (thal"a-mi-flo'ral), a. [< thala- 
mlflorous + -al.] In "hot., having the petals and 
stamens arising immediately from the torus or 
thalamus ; belonging to or characteristic of the 
TJialamiflorx. 
thalamiflorous (thal"a-mi-fl6'rus), a. [< NL. 
thalamiflorus. < L. thalamus (< Gr. Dala/io;), a 
bed, + flos (flor-), flower.] In hot., same as 
tluilamifloraJ. 
thalamite (thal'a-mlt), . [< Gr. 9a7.aiij.TtK (see 
def.), < BMauof, an inner chamber, the lowest 
part of the hold of a ship: see thalamus.] In 
Gr. atitiq., a rower of the lowest of the three 
tiers of oarsmen in a trireme. See thraiiite and 
zeugite. 
Behind the zygite sat the HuOamite, or oarsman of the 
lowest bank. Encyc. Brit., XXI. 80. 
6262 
cailia.] The cavity of the thalamencephalon; 
the thalamic ccelia, commonly known as t lie- 
third ventricle of the brain. 
thalamocrural (thaFa-mo-kro'ral), a. [< NL. 
thalliums, q. v., + crural.] Pertaining to the 
thalamns and the cms cerebri. 
Thalamophora (thal-a-mof'o-ra), n. pi. [NL., 
< Gr. ttUajUOf, an inner chamber, + -( 
. j 
tpfpeiv = E. bear 1 .] A name proposed by Hert- 
wig (1819) for the foraminifers, or those rhizo- 
pods which possess a skeleton, or which are 
invested by a chitinous test or covered by sili- 
cious or arenaceous particles: thus equivalent 
to and conterminous with Foraminifera. 
thalamus (thal'a-mus), n.; pi. thalami (-ml). 
[NL., also OuUamos; < L. thalamus, < Gr. fta/.a- 
uof, an inner chamber, a bedroom, a bed.] 1. 
In Gr. archeeol., an inner or private room; a 
chamber; especially, the women's apartment 
(Homeric); a sekos. 
The thalamos in Asiatic temples. 
C. 0. Miiller, Manual of Archicol. (trans.), 288. 
The walla of quarry-stones bonded with clay were simi- 
lar to walls which were "found by many hundreds in all 
the five prehistoric cities of Troy, in the treasuries of 
Mycenaj, in the thalainos of Orchomenos," etc. 
Appleton's Ann. Cyc., 1886, p. 34. 
2. In anat. : (at) The apparent origin of a cra- 
nial nerve ; the place where a nerve emerges 
from or leaves the brain. (6) Specifically, the 
optic thalamus; the thalamus of the optic 
nerve ; the great posterior ganglion of the cere- 
brum, forming the lateral wall of the cere- 
bral ventricle, and connected with its fellow 
by the middle commissure of the brain. See cut 
under cerebral. 3. Inbot. : (a) The receptacle 
or torus, (b) Same as thallus Anterior, infe- 
rior, internal, and posterior peduncles of the thal- 
amus. Seepeduiuile. Nucleus externus thalami. See 
nucleus. Thalamus nervi optici, or thalamus opti- 
CUfl, the optic thalamus. See def. 2 (ft). 
Thalarctos (tha-lark'tos), n. [NL., irreg. for 
T/iii/dHsarctos.] Same as Thalassarctos. 
Thalassarachna (tha-las-a-rak'na), n. [NL. 
(Packard, 1871), < Gr. ffaXaaaa" the sea, + 
apaxvr/, spider.] A genus of marine mites be- 
longing to the ffydrachnidse, a family of water- 
mites. T. verrilli is dredged in 20 fathoms off 
Eastport, Maine. 
Thalassarctos (thal-a-sark'tos), n. [NL. (also 
Thalarctos (J. E. Gray, 1825) and Thalarctus), 
< Gr. Bd^aaaa, the sea, + dp/croc, bear.] That ge- 
nus of I'rsidee which contains the polar bear, 
T. maritimus. See cut under bear 2 . 
Thalasseus (tha-las'e-us), n. [NL. (Boie, 
1822), < Gr. 6a7Jaaaei'f, a fisherman, < 8aAaaoa, 
the sea.] A genus of Sterninse, or subgenus of 
thalamium (tha-la'mi-um), 11. ; pi. 
(-a). [NL., < L'. thalamus, < Gr. 6d'/.afiof, an in- 
ner chamber, a bedroom, a bed : see thalamus.'] 
In hot., a fruit-bearing organ or cavity, (a) A re- 
ceptacle containing spores in certain algee. (6) The hy- 
incnium of fungi, or one of its forms, (c) The disk of li- 
chens. 
thalamoccele (thal'a-mo-sel). H. [< Gr. Oa'Aa- 
.uof, au inner chamber, '+ noiMa, a hollow : see 
Royal Tern ( Thalasseus ntaximHS). 
Sterna, containing those large terns whose 
black cap extends into a slight occipital crest, 
and whose feet are black. See Sterna and tern 1 . 
Thalassia (tha-las'i-a), n. [NL. (Solander, 
1806), so called from their habitat; < Gr. 6aMa- 
aia, fern, of BaUaoioi;, of the sea, < QaAaaaa, the 
sea.] A genus of plants, of the order Hydro- 
charidees, type of the tribe Th(ilassie&. It is char- 
acterized by'unisexual two-leaved one-flowered slightly 
tubular spathes, the long-pedicelled male flower with 
three ovate petaloid segments and six long erect anthers, 
the female at first nearly sessile and with a long-beaked 
ovary which matures into a globose roughened fruit de- 
hiscent into many ascending or stellate lobes. The two 
species are plants growing submerged in the sea, with long 
thong-like leaves from an elongated creeping rootstock ; 
T. teitudinum, of the West Indies, known as turtle graft 
and manattt-yrass, is a gregarious rosulate plant of the 
sea-bottom, with linear leaves about a foot in length. 
thalassian (tha-las'i-an), n. [< Gr. da7.aooios, 
of the sea, < ffa)\anaa, tie sea.] Any sea-turtle. 
thalassic (tha-las'ik), . [< Gr. Ba7.aaaa, the 
sea, + -ic.] '1. In zool., living in the high 
seas; pelagic; marine. 2. Of, pertaining to, 
or restricted to the smaller bodies of water 
called seas, as distinguished from oceanic. 
The commercial situation of the trading towns of North 
Germany, admirable so long as the trade of the world was 
thalassographic 
chiefly potamic or thalassic in character, lost nearly all 
its value when at the opening of the sixteenth century com- 
merce became oceanic. The Academy, Oct. 26, 1889, p. 265. 
Thalassic rocks. See littoral rocks, under littoral. 
Thalassicolla(tha-las-i-korii), ii. [<Gr.6d/.a.aaa, 
the sea, + IM'/'/II, glue.] Th'e typical genus of 
Thalaxxirollida'. T. ptlttgicu is an example. 
Thalassicollidae (tlm-las-i-kol'i-de), ii.pl. [NL., 
< Thakusteotla + -idx.] A family of unicapsu- 
lar or moiiocyttarian radiolarians of the order 
Peripylxa, of spherical form, with single nu- 
cleus, and the skeleton wanting or represented 
only by loose silicious spieules. Representa- 
tive genera are Tlialaxxicolla and Thalassosphie- 
ra. Also Thalassieollea. 
thalassicollidan (tha-las-i-kol'i-dan), a. and 
n. [< TlialaxHicnHidep + -an.] I. a. Pertaining 
to the Thalassicollidee, or having their charac- 
ters. 
II. n. A member of the Thalassicollidee. 
Thalassidroma (thal-a-sid'ro-ma), n. [NL. 
(N. A. Vigors, 1825), irreg. < Gr.'fld/aomz, the sea, 
+ Apo/ioc, running.] A genus of small petrels: 
formerly including those, like the stormy pet- 
rel, T. pelagica, now placed in the restricted 
genus I'rocellaria. 
Thalassieae (thal-a-si'e-e), n. pi. [NL. (Ben- 
tham and Hooker, 1883), < Thalassia + -eee.] 
A tribe of plants, coextensive with the series 
Marinas (which see). 
Thalassina (thal-a-sl'nii), n. [< Gr. Bdfaaea, 
the sea.] The typical genus of Thalassinida>, 
containing such forms as T. scorpionoides. See 
cut under Thalassinidee. 
thalassinian (thal-a-sin'i-an), a. and n. [< 
Thalasxina + -ian.] " I. a. Of or pertaining to 
the Thalassinidse. 
II. . A burrowing crustacean of the family 
Thalassinidee. 
Thalassinidae (thal-a-sin'i- 
de), . pi. [NL., < Tlialax- 
sina + -idee.] A family of 
macrurous decapod crusta- 
ceans, typified by the genus 
Thalassina. They have the po- 
dobranchiee completely divided or 
reduced to epipodites, the pleuro- 
branchiae not more than four and 
not posterior, and the branchiae 
with foliaceous as well as filamen- 
tous processes. They are remark- 
able for the length of the abdomen 
and the softness of the test, and 
are of burrowing habits. They 
are commonly known as scorpion- 
lobsters. 
Thalassiophyta (tha-las-i- 
of'i-ta), n. pi. [NL., < Gr. 
floAdomof, of or belonging to 
the sea (< Bafacaa, the sea), 
+ </>vr6v, a plant.] A name proposed by La- 
mouroux for Alg, but inapplicable from its be- 
ing too restricted excluding all fresh-water 
species. 
thalassiophyte (tha-las'i-o-fit), . [See Tlxt- 
lasniophyta.] In hot., a plant of the Thalassi- 
ophjita; a seaweed ; an alga. 
Thalassoaetus(tha-las-o-a'e-tus), n. [NL., 
orig. T/iallasoaftus (Kaup, 1845), later TJialla- 
saetus (Kaup, 1845), Thalassaetiis (Kaup, 1847), 
T/mZassae<w*(Reicnenbach,1850), <Gr. HaAaaaa, 
the sea, + afr<5f, an eagle.] A genus of sea- 
eagles, in which the tail has fourteen rectrices, 
as T. pelagicus, of Kamchatka and Alaska. 
See cut under sea-eagle. 
Thalassochelys (thal-a-sok'e-lis), . [NL. 
(Fitzinger), \Gr. 6al.aaaa, the sea, + ^t/lt'f, a 
tortoise.] A genus of chelonians, of the family 
t'lieloniidse; the loggerhead turtles. 
thalassocracy (thal-a-sok'ra-si), n. Same as 
tlialassocraty. 
We read of Minos, the legendary Cretan ruler, with his 
thalassocracy, and we think chiefly of war, not of com- 
merce yet the power of Minos would have been of little 
moment unless to protect commerce. 
Amer. Jour. Anhseol., VI. 440. 
thalassocraty (thal-a-sok'ra-ti), n. [< Gr. 6a- 
/laaaoKparia, mastery of the sea, < Ba/.aaaoKparclv, 
rule the sea, < 6d/.aooa, the sea, + uparelv, rule.] 
Sovereignty of the seas. [Rare.] 
He [Polycrates] was also the first to lay claim to the 
sovereignty of the ^Egean Sea, or thalasxocraty , which at 
that time there was none to dispute with him. 
Encyc. Brit., XXI. 249. 
thalassographer (thal-a-sog'ra-fer), H. [< th<il- 
assoyraph-ij + -cr 1 .] One who occupies him- 
self with the study of the phenomena of the 
ocean: same as oceanographer. 
thalassographic (thft-las-d-graf'ik), a. [< thal- 
i/sxn(/m/ili-i/ + -/<.] Relating to or concerned 
with thalassography : same as oce<uio<jr<tpltic. 
