CONCHIFERA. al 
25 bis, fig. 7, Cuv. R. Ani., éd. ill., Moll. Pl. 85, fig. 1; the pearl-shell. 
The shell is sometimes four-cornered, with round margin, greenish-brown 
striped with white spots, nacreous within, yellow or blueish white. This 
conchifer produces the finest pearls, and is found in the Persian gulf and 
in the Indian ocean at Ceylon and Borneo, in the straits of Malacca, 
&c. The largest pearls are found in the deepest places, as in the Persian 
gulf near the island Kharrak, where they lie on very deep banks. The 
Persian pearls are bard, and consequently more esteemed than those of 
Ceylon, which are often subject to desquamation. 
B. Dimyaria. Two muscular impressions, mostly remote, 
sometimes approximate. Ligament of valves external in most. 
Family V. Mytilacea. Mantle cloven anteriorly. Foot conical 
or tongue-shaped, byssiferous. ‘Two muscular impressions in each 
valve remote. Anterior adductor muscle often very small. 
Pinna L. Shell fragile, thin, often imbricato-squamose, elongate, 
triangular, angustate towards the points. Hinge edentulous ; liga- 
ment marginal. Animal (Chimera Pout) with foot vermicular, 
subulate, transversely rugose, delivering at its base the byssus 
of long, dense, silken filaments. Anterior adductor muscle near the 
apices, posterior larger, subcentral. A conical contractile appendage 
at the posterior part of mantle (trachea POLI). 
The shells are large, triangular, thin, and very small at the point; along 
each shell there runs lengthwise a keel-shaped eminence sometimes feeble, 
for each is formed of two surfaces that meet at an obtuse angle. The 
animal penetrates the sand with the point of the shell, and fastens itself 
above it by the byssus to other objects. The silky byssus-threads of species 
from the Mediterranean are used in Calabria and Sicily as guards for 
gloves, stockings, purses, &c. 
Sp. Pinna nobilis ., Pinna muricata Pout, Testacea utr. Sic. Tab. 34, fig. 
1, Brainy. Malac. Pl. 64, fig. 1;—Pinna rotundata L. (and P. squamosa 
GMELL., Lam.), Lister Tab. 374, fig. 215, Encycl. méth., Vers. Pl. 200, 
fig. 2, &c. Many fossil species of this genus from the secondary, and some 
from the tertiary formations are known; to the last belongs Pinna margari- 
tacea LAM., Ann. du Mus. 1x. Pl. 17, fig. 3, from the calcatre grossier. 
Mytilus Li. (in part), Bruce. Shell elongate, not squamose, 
rather smooth, equivalve, with points placed forward, hinge edentu- 
lous or with two teeth obsolete. Ligament dorsal, linear, received 
in a narrow, elongate, marginal sinus. ‘Two muscular impressions, 
the anterior very small. Animal (Callitriche Pout) with foot 
lingulate, canaliculate, byssiferous, the mantle concrete posteriorly 
