MOLLUSCA. 
372 
observable in the two valves.] The larg:e species of our coasts {Ostrea maxima, Linn.), is the Pilgrim’s shell, [worn 
in front of the hat by those who had visited the shrine of St. James in the Holy Land.] It is eaten. 
The Limae {Lima, Brug.) differ from the Pectens in having a more elongated shell, w ith shorter ears, and a 
greater inequality of the sides. The majority have the ribs raised into scales. The valves cannot be closed in the 
living state, and the cloak is ornamented with a vast number of filaments of different lengths, without tubercles ; 
and further within there is a broad fold which closes the gape of the shell, and even forms a protuberant veil. The 
foot is small, and the byssus inconsiderable. The Limae swim rapidly, by flapping their valves. One species in 
the Mediterranean, of a pure white colour {Ostrea Lima, Linn.), is eaten. 
Pedum, Brug.— The shell is similar to Lima, but the valves are unequal, and the most convex only has a deep 
sinus for the byssus. The animal also is very like that of Lima, but its cloak has only a single row of small slender 
tentacula. Its byssus is larger. The one species known is from the Indian sea. 
Certain fossils may be placed here which have the hinge, ligament, and central muscle of the Ostreae, Pectines, 
and Limae, but are distinguished by some peculiarities of the shell. The Hinnites, Defr., seem to be Oysters, or 
Clams, wdth small ears and adherent shells, irregular and very thick, especially the convex valve. There is a fossa 
at the hinge for the ligament. (Four recent species of this genus have been described.) The Plagiostomes, Sower,, 
have the oblique shell of the Limae, flattened on one side, very minute ears, the valves more ventricose, striated, 
without scales, and the outlet of the byssus less. They are found in formations older than the chalk. The 
Pacliytes, Defr., have nearly the figure of the Pectines, a regular shell with small ears ; there is a transverse flat 
space between their summits, which has a strong triangular emargination in one of the valves, through or in which 
the ligament passes or is lodged. The Bianchores, Sower., have unequal oblique valves, one of them adherent and 
perforated in the summit, the other free and eared. The Podopsides, Lam., have regular striated valves, without 
opercula : one has the apex more prominent than the other, truncated and adherent ; this apex is often very thick, 
and forms a kind of stalk to the shell. (M. de Blainville regards the preceding four genera as nearer allied to Tere- 
bratula ; and M. Deshayes, on the contrary, approximates them to Spondylus.) 
Although multivalve, we should approximate 
The Anomic, Brug., — 
To the Oysters. They have two thin, unequal, irregular valves, the flattest 
of which is deeply notched on the side of the ligament, which is similar to 
that of the Ostrea. The greater part of the central muscle traverses this 
opening, to be inserted into a third plate, that is sometimes calcareous and 
sometimes horny, by which the animal adheres to foreign bodies ; and the 
remainder of the muscle serves to join one valve to the other. The animal 
t^Echion, Poli) has a small vestige of a foot, similar to that of a Pecten, 
which glides between the emargination and the plate that closes it, and 
perhaps serves to direct water to the mouth, which is adjacent. Their 
shells are found attached to various bodies, like Oysters. They are found 
in every sea. 
[Placunomia, Sowerby, is the link which connects Anomia with the following genus. With an arrangement of the 
hinge, approaching very nearly to that of Placuna, we have the distinguishing organization of Anomia, while the 
external appearance of the shell, especially if viewed in water, bears the strongest resemblance to a Plicatula, or 
some of the plicated Oysters. The organ of adhesion resembles that of Anomia, but is inserted between the laminae 
of the internal surface of the lower valve, above the muscular impression, and below the hinge, and passes out into 
an external, irregular, somewhat longitudinal superficial fissure, or cicatrix, naiTOwest at the hinge margin, and 
which it entirely fills to a level with the surrounding surface of the shell. Three species are known, natives of 
the tropical seas.] 
The Placuna, Brug., is affined to the Anomiae, and, like them, have thin, unequal, and often irregular valves, 
but neither are perforated. On one of these valves, near the hinge, we perceive two prominent ribs, forming a 
triangle whose apex is towards the hinge. The animal remains unknown. 
Spondylus, Linn. 
These have a rough and foliated shell, like the Oysters, and frequently spiny, but their hinge is more 
complicated, for, besides the fossa for the ligament, there are two teeth in each valve that enter into 
fossm in the opposite valve respectively : the two middle teeth belong to the most convex valve, which 
is usually the left, and has, behind the hinge, a projecting flattish beak, as if it had been sawed. Like 
the Pectines, the margins of the cloak of the animal are garnished with two rows of tentacula, and in 
the outer row there are several terminated with coloured tubercles : in front of the abdomen is a vestige 
of a foot, under the guise of a broad radiated disk with a short pedicle, and capable of contraction and 
elongation. From its centre there hangs a thread terminated with an oval mass, the use of which is 
unknown. The Spondyli are eaten like Oysters. Their shells are very often vividly coloured. They 
Fig-. 186. — Anomia ephippium 
