Chap. III. 
CONCH 
Terms em- 
ployed in 
defcvibing 
Shells. 
Valves , of bivalve (hells, are divided into right and 
left, equal and unequal, equilateral and inequilateral, 
fuperior and inferior. 
. right valve (dextra), is diAinguifhed from the 
left, by placing the fhell on its bafe, having the car- 
dinal ligament before, and the. anus behind. In this 
polition the right valve of the fhell correfponds to 
the left of the observer, and the left valve (Aniftra) 
to the right of the oblerver. 
■ equal (equales), when the right valve corre 
f - -- - 
fponds with the left in form, Aze, and other external 
characters. 
fuperior (valvula fuperior). In an irrregular 
fhell, fuch as the oyiter, one of the valves is attach- 
ed to folid bodies ; the other in this cafe is fuperior. 
This valve is fometimes called by Linnaeus, the lid 
(operculum) : in fome fpecies it is flat and fmall, 
and in others more convex than the inferior valve. 
— . — keel fhaped (valvulse carinatse), when one 
part of their convexity prefents a fharp edge. 
, — — chambered (coneameratse), when they exhi- 
bit in their cavity teilaceous plates, detached and 
laifed. 
— fpinous (fpinofae), when the whole furface is 
furnifhed with fpines. 
■ banded (fafeiatae), exhibiting large coloured 
tranfverfe ftripes or bands.! 
. lamellated (lamellofae), when the furface is 
furnilhed with plates more or lefs feparated. 
— — • — radiated (radiatae), exhibiting divergent or 
coloured rays. 
— — finuated (lacunofse), when one of the valves 
has a fenfible depreffion at the middle of its mar- 
gin, and a correfponding elevation of the oppofite 
valve. 
— — ftriated (Ariatse) when the furface is marked 
with Arise. 
<- — — — tranfverfe, when the Arise are parallel to the 
margin of the valves. 
■ longitudinal, when they run from the bafe to 
the circumference. 
Mufcular imprejjlons (impreffiones), are marks on the 
interior furface of the valves, where the mufcles of 
the animal are attached. 
— folitary (folitarise), when the inner furface of 
each valve has only one. 
— — - double (duplicatse), two on the inner furface 
of each valve. 
■ triple or ternate (ternatse), three in each 
valve. 
Ligament (ligamentum), is a horny fubAance, of little 
flexibility, which unites the two valves near their 
bafe, and which in almoA all bivalve fhells is placed 
at the lower part of their anterior furface. It is di- 
vided into. 
gaping (hians), when its upper extremity is 
divided into two. 
— — — double (duplex), when under the external li- 
gament there appears a fecond, in a particular hol- 
low of the hinge, which does not appear externally. 
internal (internal), when it unites the valves 
without appearing externally. 
— — ■— ■ profound (retraCtum feu intraCtum), when it 
is fo deep in the future as fcarcely to be feen when 
the valves are fhut. 
OLOGY. 
■ truncated (truncatum), when fhorter 
future. 
Furrows (fulci), are thofe impreflions or interAices 
between the ribs or rays on the furface of the i 
valves. 
fquare (quadrati), when the bottom is flat. 
— lamellated (lamelloii), when the bottom is 
marked with fmall tranfverfe feales. 
• punctated (excavate punCtati), when the whole 
397 
than its Terms em- 
ployed in 
deferibing 
Shells. 
furface is marked with fmall cavities or dots. 
3. Explanation of Terms applied to Univalve Shells. ^ 
The bafe , (bafls) is the moA elevated part of the Univalves, 
fhell, oppofite to the fpire. It is divided into, 
notched (emarginata), when it is accompanied 
with a deep notch. 
■ — tubular (tubulofa feu cordata), when it is form- 
ed by a tube. 
n — Ample or entire (fimplex aut integra), without 
notch or tube. 
Summit (vertex) Agnifies the top of fome patellae, and 
from its poAtion is central, marginal, or fubrnar. 
ginal. 
The Jbeil (teAa) is divided with regard to its poA- 
tion into fuperior and inferior. 
The anterior part (pars antica), is that which forms the 
fpire of the fhell ; and it is alfo the fuperior part. 
The form of fhells is 
- — - — - bordered (margin ata), when the two Ades of 
the opening are broader and thicker than the reA of 
the diameter. 
chambered (polythalamia), when it is inter- 
nally divided by different partitions parallel to the 
opening. 
■ ■ ■ ■ — — convoluted (convoluta), when the fpires turn 
round a lengthened cone, nearly vertical to each 
other. 
————— rooted (radicata), when it is attached to a fo- 
lid body by a ligament proceeding from its bafe. 
— — - interrupted (interrupta), when the fucceffive 
additions to the fhell are marked with diAinCt 
rings. 
— — umbilicated (umbilicata), when the axis round 
which the fphere turns, being empty, forms a cavi- 
ty at the bafe of the fhell, whofe diameter is at leaf! 
a Axth part of that of the fhell. 
imperforated (imperforata feu exumbilicata), 
when its inferior axis has neither hole nor umbili: 
cus. 
— oval or elliptic (ovales), the longitudinal dia- 
meter exceeding the tranfverfe, and the two extre- 
mities equal and a little contracted. 
— — — — egg-fhaped (ovata), the longitudinal diameter 
exceeding the tranfverfe, and the extremities termi- 
nated by the fegment of a circle. 
— — — — beaked (roArata), when the two extremities, 
fometimes tubular, form a projection in form of a 
beak. 
— imbricated (imbricata), when the furface is co- 
vered with parallel feales, fo arranged as to cover 
each other. 
turbinated (turbinata), when the belly of the 
fhell is large in proportion to the fpires, which feem 
to proceed from its centre. 
Opening 
