TURTLES

	There are countless breeds of animals throughout the world that we refer to as turtles. One of the most fascinating categories of these is the gigantic sea-turtle and his cousins.
    All of the tropical and semi-tropical seas of the globe are inhabited by huge turtles, but with this great distribution, we find a peculiar condition relating to the number of species.  Over these vast stretches of ocean, stupendously rich in their variety of life--invertebrates, fishes, a large number of marine serpents, innumerable birds and many mammals--the chelonians are limited to five species; with the exception of one, each species occurs in the warmer waters of both the Old and the New World; thus a list of the North American reptiles must include those marine turtles that are found in the vicinity of
our coasts.
    While normally inhabiting the waters of the warmer latitudes, the sea turtles are often enticed northward, along our eastern coast, by the mild currents of the Gulf Stream; during the mid-summer months they enter the northern harbours and live comfortably enough, but during the approach of cold weather these wanderers become chilled and stupefied, and fall an easy prey to fishermen.  Benumbed during the fail hurricanes, they are battered and cast lifeless upon the beaches of Long Island, Connecticut and Massachusetts, and by the very storms that originated over their native seas.  Most of the big Leatherback Turtles in our northern museums, have met a fate like this.
    Classification.--The marine turtles are divided into two families.   From a standpoint of relationship, these families are widely separated; the classified list of the families and genera of North American turtles and tortoises, in the preceding pages, will show the proper standing of these reptiles.  The Leather-back Turtle,  (Spbargis), seems to be the survivor of an extinct group, and must be placed in a family by itself, while the  Loggerheads,  the Green Turtle  and  the Hawk's-bill Turtle  are  examples  of  evolution  from  the modern, fresh-water chelonians; development along the line of adaptation to a strictly marine life has produced a highly specialised form, but the shielded carapace and plastron, and other parts of the structure, show close relationship with the Testudiniae.  Thus the student will appreciate that the family Spbargidceine species, and the Cbelonidce--four species, are not alone widely separated in classification, but appeal to one another only in a form that is essential to the life the species lead. With this understood, it is not inappropriate to embrace all the sea turtles in a chapter by themselves.  This arrangement popularises the subject and makes it possible to construct a general key.

MUSK OR MUD TURTLES



    All of the species of the small family Cinosterniae, bear a general resemblance to one another.  They are of small size-few attaining a length of five inches.  The upper shell is bluntly oval in outline, rounded above, and possesses no trace of the flaring edge, or scolloped border as does the shell of typical pond and river turtles.  It might be said that the carapace of these turtles looks like a smooth, flat stone.  The under shell-plastron--is a distinguishing character.   It is composed of a broad, rigid bridge, and two hinged, movable lobes, that may be drawn up against the carapace--slightly so with Aromochelys, but to such an extent with Cinosternum, that the species of the latter genus have sometimes been called "box turtles," an appellation which rightly belongs, however, to a genus of strictly terrestrial turtles (Cisludo).
    Classification and Distribulion.--But two genera constitute this family.  Aromocbelys appears to be represented by three species, all of which occur in eastern North America.  The larger genus, Cinosternum, comprises about eleven species, six of which inhabit the United States and northern Mexico; one occurs in Mexico generally except the northern portion, three in Central America, and one in northern Brazil and the Guianas. The structural differences of these species are but slight, and in technical nomenclature described principally from the shape of the shields forming the plastron.  The greater number of the species of both genera display much the same colouration of the upper and lower shells.  .Some slight characters are exhibited in the markings of the head.  Generally speaking, it must be explained that many of the species are very difficult to determine. As a large series of specimens demonstrate that the characters of the plastron are subject to considerable variations, it is possible that the present number of species will be condensed, after further investigations.
    The student is advised to carefully examine the plastrons (lower shells) of the species figured and to become familiar with the distribution of these turtles.  By working in this fashion the determination of specimens is rendered systematic and the detailed descriptions will impart their references in a thoroughly comprehensive manner.
    All of the Cinosterniae are thoroughly aquatic, frequenting slow-running streams or muddy rivers, from which they seldom venture.  In such places they are admirably protected by their dull, mud-coloured shells, which are often coated with moss. These turtles exude a strong and musky odor when annoyed. They are much disliked by persons who fish in fresh-water, as they will greedily take a hook and perform such antics in the water that the sportsman is often lead to anticipate that he has captured a fish of prodigious size.  When handled, they snap and bite fiercely, and, in fact, represent in miniature the actions of the formidable snapping turtle.