66 MUREX. 
MONO'ICA. Bl. Second sub-class of the class Paracephalophora, 
Bl. divided into the orders Pulmobranchiata, Chismobranchiata, 
Monopleurobranchiata, in the first section; and A porobranchiata, 
Polybranchiata, Cyclobranchiata, Inferobranchiata and Nucleo- 
branchiata, in the second. 
MONOMYA‘RIA. Lam. (Movos, monos, single; pov, myon, a 
muscle.) The second order of Conchifera, consisting of those 
bivalve shells which have but one principal muscular impression 
in each valve. The Monomyaria are thus divided: First sec- 
tion, families Tridacnea, Mytilacea, Malleacea; second section, 
families Pectenides, Ostracea; third section, families Rudistes, 
Brachiopoda. 
MONOPLEUROBRANCHIA’TA. Bl. The second order of the 
first section of Paracephalophora Monoica, Bl. containing Fam. 
1, Subaplysiaca; 2, Aplysiaca; 3, Patelloidea; 4, Acera. 
MONOPTYG™MA. Lea. A genus of small fossil shells resembling 
Tornatella, but having a strong, oblique fold in the centre of 
the columellar lip. M. Elegans, fig. 344. 
MONOTHALA'MIA. (Movos, monos, single; @adapos, thalamos, 
chamber.) The second division of Cephalopoda, Lam. contain- 
ing only one genus, viz. Argonauta. 
MONOTIGMA. Gray, fig. 371. 
MO’RIO. Montf. Cassiparia, Auct. C. Echinophora, fig. 407. 
MULINIA. Gray. A genus composed of species of Macrra, . 
Auct. described as having the ligament (properly so called) in- 
ternal, and lateral teeth simple. Ez. fig. 82. M. bicolor; Mactra, 
Auct. 
MULLE'RIA. Fer. Fam. Ostracea, Lam. Deser. Irregular, sub- 
quadrate, inequivalve, inequilateral, foliaceous, attached, pearly 
within, green, horny without; hinge irregular, with a partly 
external ligament passing to the interior through a sort of sinus. 
Obs. This remarkable shell resembles Etheria, in general form 
and appearance, but is distinguished by having only one muscu- 
lar impression. It isso rare that, although not very beautiful, 
a specimen has been known to fetch £20 at a sale. Fig. 192. 
MULTISPYRAL. (Multus, many ; spira, spire.) Applied to a shell 
when the spire consists of numerous whorls; or to an opercu- 
lum of numerous volutions. 
MUL'TIVALVE. (Multus, many ; valva, valve.) Consisting of nu- 
merous valves. There are three kinds of Multivalve shells; 
Ist. Those in which the valves are arranged in pairs, and pro- 
duce a flattened figure, as pedunculated Cirripedes, fig. 34 to 43; 
2nd. Those in which they are arranged circularly, as Sessile 
Cirripedes, fig. 14 t033; 3rd. Those in which they are arranged 
in a straight line, as Chiton, fig. 227. 
MU’REX. Auct. (A sharp rock.) Fam. Canalifera, Lam. Sipho- 
nostoma, Bl. Descr. Turrited, ventricose, thick, with three o1 
more longitudinal, continuous, branched, spinose, or fringed 
