The Chitons Coat-Of-Mail Shells - Order Poly Placophora

The Californian coast is the best place to study chitons alive. The greatest variety to be found in any one region is 238 The Chitons. Coat-of-Mail Shells assembled here, including some of the largest and most brilliantly coloured forms.

The Showy Chiton (I schnochiton conspicuus, Cpr.) is a large and beautiful chiton found from Santa Barbara to Magdalena Bay It is three to four inches long, the shell shaded green, and finely _granulated, pink at the umbo of each valve, and smooth. Faint wavy bands sculpture the lateral areas; the girdle is narrow, and coated with bristles set so close as to form a velvety cover. The front valve is concave.

The Gray Chiton (I. Magdalenensis, Elds.), a smaller species with much the same range, is also found at Santa Catalina and Santa Barbara Islands. It is pale green underlaid with pink, and mottled, with radiating riblets, and the central areas have small diamond-shaped pits. The first valve is flattened, not concave, in front. The girdle is covered with fine, close scales. The foot projects forward, covering the head.

In studying the development of this species Heath found that the eggs were laid in gelatinous strings almost a yard in length, the average number of eggs contained in each string being 115,94o. When six days old the young chitons enter upon the free-swimming period of their existence. This lasts but two hours. After it is spent, they settle down upon rocks or seaweed and undergo a gradual metamorphosis.

During all the stages of development passed up to the time of settling down the chiton exhibits radial instead of bilateral sym metry The embryology of Annelid worms is similar. This seems to point back toward a common ancestor of these two groups.

The Magnificent Chiton (Chiton inagnificus, Desh.) has a very large black shell, with minute blue dots scattered over it, and a blue lining. The surface of the back is smooth, with faint radiat ing lines. The girdle is narrow, made of shiny overlapping black scales. This handsome, smooth-shelled chiton attains the length of four or five inches, with a breadth of three inches.

Habitat.— Chilian coast.

C. Goodallii, Brod., is a large smooth chiton, often fully 'six inches long, with straight sides sloping up to a central peak, like the roof of a house. The colour is dark brown, the narrow girdle paler brown, made of flat overlapping scales. The lateral areas of the middle six valves are crossed by dark con centric bands or terraces. These indicate rest stations at which 239 The Chitons. Coat-of-Mail Shells

growth ceased, and was resumed later. The interior of these shells is white.

Habitat.— Galapagos Islands.

C. squamosus,

Linn., often three inches long,is a shdwy species from the West Indies. The ground colour is: huff with olive tinge; the median areas of the valves are longitudinally, banded with black. The lateral areas bear radiating lines of very small beads, running outward from the limbo. There is a dark blotch on each side of the keel. The girdle, is scaly like snake's skin and banded alternately with dark and light olive green. The interior of the shell is dark blue green.

Three little chitons under an inch in length are found on rocks between tide marks on our Atlantic coasts. They. are• C. ruber, reddish in colouring, C. alba, with whitish shell, and. C. apiculatus, with bristly points on shell and girdle. The first two species named are also found on rocks and seaweeds on the coasts of England. Iceland, too, has its chitons.

The Iceland fishermen believe that if these "sea-bugs," as they, call them, are swallowed raw they will prevent sea-sickness and also quench thirst. 1 t is probable that the cure would prove, worse than the disease for most people' who cross the ocean.—Baker.

The Mossy Chiton (Mopalia mucosa, Gld.) has two oblique slits, one on either side of the median one, in the posterior valve. The girdle is narrow and densely covered with short curling hair. The plates are brown and sculptured with lines of intersecting riblets on the lateral areas. Sometimes the colour is bright orange, scarlet or green. Occasionallyit is gray. Length, 2 inches.

Habitat.--Pacific coast to San Diego, Cal.

Katherina tunicata,

Sby., represents a closely related genus.

The Giant Chiton (Cryptochiton stelleri, Midd.) has its valves completely covered by the leathery girdle. It lives along out west coast, just below the low water mark, a striking object with its brown surface thickly studded with bright red' spines. It varies considerably in colour. It is from six to eight inches long, oval in form, with rounded back, flat or concave under neath with a strong pedal surface attaching it to rocks. The buried valves are pale and hard, without the usual porous layer. They are the beautiful pink "butterfly shells" people pick up on shore.

The Indians and Aleuts eat the fleshy parts of this mollusk raw. Habitat.— Japan to Santa Barbara Islands, California.

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