CHELONIA. 



re neither orbital nor temporal !*. The parietal bones, which 

 form above a groat rectangle, unit* by their defending portions to 

 the palatine*, the ptorygoideans, the petrous, and the upper occipital 

 bone*. They form by themselves nearly the whole roof of tin- 

 cranium. Following the pterygoidean, the temple is bounded behind 

 by the tympanic bone or the* tympanic cavity, which resembles in 

 part a trumpet. The frame of the tympanum is complete. A hole 

 in the posterior wall suffers the oniculum to pass into the second 

 chamber, which, in the skull, is only a long groove of the posterior 

 urfaoe of the cavity, wliich terminates in a hollow, in the formation 

 of which the petrous bone, the external occipital, and the lateral 

 occipital concur. It is not closed behind, except by cartilage and 

 membranes ; and in the wall of the aide of the cranium are pierced 

 the two fenestno, as ordinarily. Above this hole of the first chamber, 

 by which the oniculum passes, is another which conducts into the 

 mastoidean cellule, which, on account of the outward projection of 

 thr tympanum, is found within and not behind. The occipital spine 

 is a short vertebral crest, and the mastoidean tubercles are transversal 

 crests, which belong entirely to the mastoidean. Even in large 

 individuals the six occipitals ordinary to the tortoises may be distin- 

 guished. Below, the smooth and nearly plane cranium presents a 

 sort of regular compartment, formed of the intermaxillaries, the 

 maxillaries, the vouier, the palatines, the pterygoideans, the sphenoid, 

 the petrous bones, the tympanic cavities, the baxilary, and the lateral 

 and external occipital*. Behind the ceiling of the temple the petrous 

 bone forms a square compartment between the pterygoidean, the 

 tympanic cavity, the external occipital, the superior occipital, and 

 the parietal bones. 



The lower jaw of the tortoises is divided in a manner which it is 

 not very easy to refer to that manifested in the crocodile, to which, 

 Cuvier observes, that of the birds has a much more striking relation ; 

 but the bird's jaw, he adds, also approaching to that of the tortoises, 

 aids us in referring it to a common type. The space occupied in the 

 crocodile by the two dental and the two operculnr bones is filled in 

 the Marine Tortoises, the Fresh- Water, and Land-Tortoises, as well as 

 in the Trionycet, with a single bone only, the analogue of the two 

 dental bones. Cuvier never saw in all these sub-genera, even in their 

 youth, any trace of symphysis: the bone is continuous in the tortoises, 

 as in birds. The Matainatu, or C/ulyt, on the contrary, preserves in 

 every age a division at the anterior part. The opercular bone always 

 exists, as in the crocodile, at the internal surface ; but it is carried 

 farther backwards, and attains to the posterior extremity. Beneath it 

 is the angular lioiie forming the lower edge of the jaw. That which 

 Cuvier names the surangular bone occupies the external surface of 

 this part of the jaw, and proceeds also to its posterior extremity, 

 but only touches the angular bone quite behind, and in becoming 

 separated on the two anterior thirds by a long point of the dental 

 bone. Above, and towards the back part, between the opercular and 

 surangular bones, the articular bone is situated, as in the birds ; but 

 in the tortoises it is reduced to smaller dimensions, only serving for 

 the articulation and for the insertion of the depressor muscle, or the 

 analogue of the digastric muscle. The coronoid apophysis does not 

 belong at all to the surangular bone in this order, but to a bone placed 

 between the dental, the opercular, and the surangular bones ; and in 

 front of the aperture by which the nerves enter the jaw, an opening, 

 which is here found at the upper border, instead of being, as in the 

 crocodile and the birds, at the internal surface. This bone, which is 

 not found in the birds, can only respond to the complementary bone 

 in the crocodile. Cuvier saw in the Emyi csparua the surangular, the 

 opercular, and the articular bones anchylosed, and their sutures 

 effaced, at a period when all the others were still visible. The 

 general form of the bony jaw corresponds nearly to what is seen 

 externally. More pointed in the Triunyca and Chflune Caretta ; more 

 obtuse, more parabolic, in 6'. Hydai and the Land-Tortoises ; semi- 

 circular in front of the coronoid apophyses in the Matamata ; it differs 

 also in the furrow with which it in hollowed. This furrow is narrow, 

 deep, and equally wide in the I>and-Tortoises ; widens and deepens 

 towards the symphysis in C. Mydat; and is entirely wanting in 

 Trvmyi, C. Cartlla, Ac. 



The o* hyoides of the tortoises is more complicated than that of the 

 crocodiles, and varies singularly in form from one genus and even one 

 species to another. It is in general composed of a body itself, some- 

 times subdivided into many pieces, and of two, sometimes three pairs 

 of horns : and under the anterior part of its body is, besides, suspended 

 a bone or a cartilage, sometime* double, which is the true bone of the 

 tongue analogous to that seen in the birds, but articulated in them in 

 front of the body of the oe hyoides, whilst in the tortoises it in sus- 

 pended below it The greatest horns (the anterior pair when there 

 are only two, the middle when there are three, representing the 

 tyloideau bones) embrace the oesophagus, and mount behind the 

 muscles which are the analogue* of the digastrics, or depressors of 

 the lower jaw, but without being fixed otherwise than by their pro) XT 

 muscles. The Land-Tortoises have the body of the os hyoides w -ider, 

 itfl anterior portion longer, and want the small anterior horn*, whilst 

 the anterior angle is very much developed. In the miilille of the dixe 

 are two round spaces, which in certain tortoises, the Trttu'l /./>< fur 

 example, are only more delicate ; but which in the others, Tcttmlo 

 radiala for instance, are absolutely membranous. 



In some Fresh-Water Tortoises, Tatudo Europaa and T. ciatua for 



example, the body of the bone is longer than it is wide ; and has 



in ^>e front a small membranous space, and at iU anterior angles 



; the small lateral horns. Sometimes two or even four osseous nuclei 



are there formed. 



The os hyoides of Triamyjc differs still more. Its body is composed 

 in front of a cartilaginous point, un<K>r which is suspended a great 

 lingual oval cartilage. At the base of this a rhomboidal osseous piece 

 I adheres on each side, which piece represents the anterior horns, and 

 afterwards four others forming a thick dixc, concave above, wider 

 in front, and notched on the sides and behind. At the anterior 

 angles of this disc adhere the middle hornx, and to the po 

 angles are attached the posterior horns : all four are very bony. The 

 middle are formed by a long piece, which i~ compressed, arched, and 

 terminated by a small cartilage. The others are wider, flatter, and 

 prolonged by a cartilage, in the substance of which are encrusted in a 

 row from five to six bony nuclei, which are round or oval, very hard 

 and very distinct; so that the entire bone comprehends twenty 

 different osseous pieces, which appear to remain distinct to old age. 



The most singular of all these is that of the Chclyt, and is very 

 early entirely ossified. Its body is composed of a long narrow ) ris- 

 matic piece, hollowed above by a canal where the trachea runs. In 

 front this piece is dilated, and carries on each side two angular por- 

 tions, four in all, without counting the piece itaelf. The two interme- 

 diate ones unite in front, leaving between them and the principal body 

 a membranous space on which the larynx reposes. The lateral por- 

 tions, Cuvier observes, represent perhaps the small anterior horns. It 

 is on the angle which they form with the dilatation of the principal 

 body that the middle horns are articulated ; these last are \ . ry 

 strong, prismatic on their internal moiety, ami then slender, and ter- 

 minated by a bony and pointed piece, distinct from the rest of the 

 horn. The posterior horn* ore articulated at the posterior extremity 

 of the prixm formed by the principal body. They are long, strong, 

 slightly compressed, and curved into an arch. 



Under the anterior and dilated part i H'p> n, l< . I the true bone of 

 the tongue, formed in front of a semicircular cartilage, ami behind of 

 two bony pieces in form of a crescent, the internal angle of which ix 

 prolonged into a sort of tail or pedicle, which lies under the prismatic 

 body of the os hy " 



In the Turtles, C'kelvnc Caretta for instance, the body of the bone 

 is in the form of an oblong buckler, concave above for the support of 

 the larynx and the commencement of the trachea, and drawn out in 

 front into a point which penetrated into the flesh of the tongue in 

 passing upon the lingual bone. It presents on each side an angle for 

 carrying the anterior horn, which is very small ; the great horn curved 

 into an obtuse angle for going round the rcsophagus and jaw, more 

 bony than all the rest of the apparatus, is articulated to the middle of 

 the lateral border of the body of the bone, and itx free or tipper extre- 

 mity is terminated by a small cartilaginous articulation. The )>osterior 

 horns are articulated to the posterior angles. They are cartilaginous, 

 flat, rather wide, and scarcely arched. 



Bones of the Trunk : Dorsal Buckler, or Cara|>ace. The wide dif- 

 ferences prevalent in the modification and arrangement in the bones 

 of the head in this order lead one to expect, as the great French zoolo- 

 gist observes, proportional differences in the rest of the skeleton. The 

 cranial differences are, as he remarks, greater perhaps than obtain 

 among th'e whole of the mammals, and most certainly are more 

 extensive than can be found in the whole class of birds. 



The general distinguishing character of the Tortoises, that which 

 separates them from all the Verlebrata, is the external position of the 

 bones of the thorax, cm. -lopim,' with a cuirass or double buckler the 

 muscular portion of the frame, and serving also as a protection for 

 the shoulder-bones and the pelvis. 



The dorsal buckler is principally formed of eight pairs of rilw, 

 united towards the middle by a longitudinal succession of angular 

 plates, which adhere to the annular parts of so many vertcl 

 even form a part of them ; but it is remarkable that these annular 

 portions alternate with the body of the vertebra?, and do not com 

 directly with them. 



The ribs are inlaid by means of sutures into these plates ; they are 

 also united with each other, on the whole or a part of their length, 

 according to the species, and even in each species according to the 

 ages of the individuals. There are eight anterior vertebra; which do 

 not enter into this conjunction. The first seven (the ordinary cer- 

 vical) are free in their movements. The eighth, which may be 

 regarded as the first dorsal, is placed ol<li.|u> 'Iy between the last 

 cervical and the first of the fixed vert<-l>r.e of the dorsal bin ll< r, 

 which shortens it anteriorly; behind, its spinous apophysis is elon- 

 gated, and enlarges a little to attach itself by synchondrosis to a 

 tubercle of the first of th plates of the intermediate series of the 

 plastron. 



The first of these fixed vertebra:, which is the second dorsal, is still 

 rather short, and carries also its proper annular part, the npiuous 

 apophysis of which, shorter than the preceding, attaches itself to the 

 second plate by a cartilage. This second plate, narrower than the 

 first, forms but one bone with an annular part which is'below, and of 

 which the anterior portion is articulated by two small apophys, 

 the articular apophyses of the second dorsal. Thin, properly speaking, 



