Plate 85. 
MOLLUSCA. ACEPHALA. ASCIDIA. 
1. The Pearl-Oyster, Avicula Margaritifera, is found at a considerable depth in the 
waters of the Indian Ocean, Persian Gulf and off the coast of California, the best pearl- 
fishery being in the Persian Gulf, where some 30,000 persons are engaged in it. Thé best 
pearls are formed in the muscular part of the shell or in the body of the fish itself; the 
number present in a single individual varying considerably, as many as 150 having some- 
times been found. 
2. The Common Oyster, Ostrea Edulis, has a thick, irregular shell, which it has the 
power of attaching to rocks and other objects in the water by means of an adhesive sub- 
stance, which it exudes. Its powers of reproduction are incredible; one single oyster being 
able to bring forth upwards of a million young ones in the course of a year. The oyster 
is diffused over the Adriatic, the western part of the Mediterranean, the Atlantic seaboard 
northwards to the Norwegian coast, being artificially cultivated wherever practicable. This 
is done by dredging for the ‘spat’ or spawn and transferring it from the open sea to ar- 
tificial beds, expressly constructed for the purpose, where the fish are properly fed and 
fattened for market. They are a most nutritious delicacy, and in Europe alone several 
hundred millions are consumed annually. 
3. The Scallop, Pecten Jacobeus, has a beautifully ribbed shell, which is much used 
as an ornament. In the olden time it was used as a badge by the pilgrims returning from 
the Holy Land. The thickened borders of the lobes of the mantle are furnished with several 
rows of fleshy cilia, between which are regularly disposed a series of bright, smooth oculi- 
form tubercles. 
4, The Spondylus Americanus is distinguished by the long spines covering the outside 
of the shell. This genus seldom moves away from the spot where it has once attached 
itself, so that in course of time the accumulations of ooze render both the form and color 
of the shell almost undistinguishable. 
5. The Venus Papilionacea is a beautiful specimen of the extensive family of the Vene- 
ride. The shell is symmetrical and beautifully colored in many of the varieties. The animal 
burrows into the sand or ooze, projecting its breathing tubes up into the clear water. 
6. The Cytherea Gibbia, also nearly allied to the family of the Veneride by the form 
of its shell, is a beautiful specimen of this genus and is found in every sea. 
The Cockle, Cardium Echinatum, is very common on the coasts of Great Britain 
and is much esteemed as an article of food. It has a very long foot, bent like a knee in 
the middle, which serves both for the purpose of progression and for excavating holes in 
the mud and sand in which it lives. 
8. The Razor-shell, Solen Vagina, has a long, narrow, sheath-like shell and a long, 
conical foot, with which it burrows in the sand like a mole. This it will do very rapidly 
when pursued. This genus is very common in the Mediterranean. 
9. The Arca Laurata has a rather irregular and deeply furrowed shell. It is very 
commonly found on the sand and beach, and is used as an article of food in many parts. 
10. The Hammer-Oyster, MJalleus Vulgaris has a most peculiarly shaped, foliated shell, 
like a T or hammer, the interior of which is covered with mother of pearl. It is found 
in the seas of the East and West Indies attached to the rocks by its byssus or beard, 
which grows from the hinge of its shells. — 
The Salpacea are delicate, transparent animals, enclosed in a shell, through the pos- 
terior aperture of which it sucks in the water, ejecting it by the anterior one, thereby pro- 
pelling itself through the water tail foremost. The strangest peculiarity of the Salpacea is 
however that the young ones do not resemble their parents, the original form only reap- 
pearing in the next generation. For instance, one generation will appear aggregated together 
in long chains; these however produce only isolated individuals differing in form, which in 
their turn reproduce the chain-form. 
11. The Salpa Maxima — an isolated individual. This species is endowed with phos- 
phorescence, — 
The Ascidians, Ascidie, only exist as locomotive animals for a short time; moving 
about like a tadpole by means of a vibrating tail. A ‘ter a while they attach themselves to 
a submarine plant or rock, the tail disappears and they remain fixed, like fungi, their bo- 
dies being covered with irregular excrescences. The leathery external mantle encloses a 
second mantle, which contains the various organs and only adheres to the former near the 
orifices. The Ascidians are found in all seas and are divided into two classes — compound 
and solitary. 
12. The Cynthia Papillosa — a solitary individual. 
