CHELONIA. 



CHELONIA. 



986 







is the annular portion of the third dorsal vertebra; but the body of 

 this third vertebra is only articulated by its anterior moiety with the 

 posterior moiety of this third annular part, and by its posterior moiety 

 it is articulated to the anterior moiety of the fourth annular portion ; 

 aud this alternative continues, so that the body of the fourth vertebra 

 responds to the annular portions of the third and the fourth, the body 

 of the fifth to the annular portions of the fourth and fifth, and so on 

 to the tenth. 



But it is necessary to distinguish in the ribs the plate included in 

 the buckler, and a small branch which proceeds from its lower sur- 

 face, and which represents what is termed the head of the bone in the 

 ordinary ribs. This head is always articulated between two bodies of 

 vertebnc. The first of all these ribs has only this small branch, with- 

 out having any plate belonging to it in the buckler, excepting only in 

 some of the Einydes, where may be seen, between the first and second 

 longitudinal plate, and the first or second widened rib, a small piece 

 which can only represent the enlarged portion of this first rib, but 

 which does not belong to its head. It is articulated between the 

 eighth vertebra or first dorsal, and the first fixed vertebra, and by its 

 other extremity applies itself to the internal surface of the second rib. 

 This last has a plate which incorporates itself by its anterior border 

 with the first of the longitudinal series, by its spinal border with the 

 second piece of that series or the annular portion of the third vertebra, 

 and by its head between the body of the second vertebra and that of 

 the third. The succeeding ribs observe the same law, are articulated 

 by means of their head between the body of one vertebra and that of 

 the succeeding vertebra, and incorporate themselves by means of their 

 dilated part with the plate which represents the annular portion of the 

 second of these two vertebra) : and this, Cuvier observes, is a return 

 to the general law ; for in man and in the quadrupeds the ribs are 

 articulated by their head between two vertebrae, and by means of 

 their tuberosity, with the transverse apophysis of the second of the 

 two. The dilated portions of the ribs of the tortoise, in the part 

 where they are incorporated with the plates of the longitudinal series, 

 represent, then, the tuberosities of the ribs of mammals. The ninth 

 plate of the longitudinal series, which belongs to the tenth dorsal, is 

 the last with which a pair of the dilated ribs is incorporated ; and this 

 last is the ninth in all, or the eighth of those which enter into the 

 composition of the dorsal buckler. It is directed from its posterior 

 border backwards, and embraces again the succeeding plates, with 

 the external edges of which it becomes incorporated : but these three 

 plates do not, any more than the first, serve to complete the vertebral 

 canal. 



The tenth rib, attached between the bodies of the tenth and 

 eleventh vertebra;, produces no plate and enters not into the com- 

 position of the dorsal buckler. Like the first, it has only a portion 

 of the head, and is joined by its other extremity to the internal 

 surface of the ninth. 



The eleventh vertebra after the cervical is the only one that can 

 be termed lumbar ; it carries no rib. In the Turtles, its annular 

 portion again gives a plate to the longitudinal series of the dorsal 

 buckler, and is the tenth and the smallest of the pieces of this series. 

 The twelfth and thirteenth vertebrae are the sacral. At their sides 

 are attached two lateral pieces sufficiently similar to the heads of the 

 ribs, but stronger, especially the first, and convex at the end, in order 

 to their union with the posterior and upper angle of the ossa ilii. 

 Their annular portion is close and complete, and is not incorporated 

 with the plates of the buckler which follow that of the eleventh 

 vertebra. The vertebrae of the tail are free, like those of the neck : 

 hence the plates of the longitudinal series, which follow the tenth, 

 do not adhere to the vertebras, and, if they belong thereto, only so 

 belong by a metaphysical relation, and accordingly they may be 

 considered aa having been dismembered. So of the first of all the 

 plates of the series. It only furnishes an attachment to the annular 

 portion by synchondrosis, otherwise close and complete, of the first 

 dorsal vertebra ; and if one would regard it as belonging thereto, it 

 would be necessary to consider it as dismembered. 



The Turtles have three longitudinal plates after the tenth, making 

 thirteen in all ; but the second is sometimes divided into two, and 

 the ninth also, which increases their number to fifteen. 



Cuvier found fourteen in some of the Emyde*, the Emys terrain for 

 instance ; but the eleventh aud twelfth, he adds, are very small in 

 them. There is but a single one after the tenth in the Land- Tortoises 

 and the Chelydu, so that they have only eleven in all. It sometimes 

 tiagipcno that one or two of these plates are not seen externally. 

 Thus in the Box-Tortoises, the two ribs of the last pair are joined to 

 each other, and thus cover the ninth plate ; and in this respect many 

 mollifications occur in the same species; of which Bojanus has, in 

 his third plate, given many examples taken from the European 

 Tortoise. 



In Ckelyt the last and penultimate rib are attached to the eighth 

 plate, and the ninth remains hidden. In both cases the tenth aud 

 the eleventh subsist as ordinarily. 



In the Turtles, the eight pairs of ribs and the thirteen plates of 

 the longitudinal series fonn a slightly convex oval buckler, a little 

 narrowed backwards. The ribs are not incorporated throughout 

 tin ir length, a narrow fraction remains towards their exterior, and 

 the intervals between this portion and that of the anterior and 



Carapace of Trionyx, seen fiom below. 



posterior ribs are filled up by a cartilaginous membrane only. It is 

 only in extreme old age that some are widened to the end. Cuvier 

 had sometimes seen the first three and a part of the fourth in this 

 state. 



In the Fresh-Water Tortoises and in Chdys the buckler is entirely 

 filled up in time, and the ribs incorporate themselves throughout 

 their length, between each 

 other and with the marginal 

 pieces. The ossification pro- 

 ceeds still faster in the Land- 

 Tortoises, and it is only in 

 their youth that vacant spaces 

 are observed between the ex- 

 ternal parts of their ribs. 



The Sternum Plastron, or 

 Breast-Plate is always com- 

 posed of nine pieces, of which 

 eight are pairs, and the ninth 

 is odd and always placed be- 

 tween the four anterior ones, 

 with the first two of which 

 it generally coheres, when 

 it is not articulated with the 

 four. 



These nine pieces vary much in figure according to the genera and 

 species. 



In the Land and Fresh- Water Tortoises and in Chdys they only 

 leave vacancies between each other in early youth, when they are 

 formed by bony rays shooting in various directions iti the still 

 cartilaginous disc of the plastron, like the bones of the cranium in 

 the foetus of mammals ; but, with age, these rays join each other 

 from every side, and form a disc compact in all its parts, which 

 unites itself by a more or less considerable extent on each side to the 

 dorsal buckler. 



In the Turtles, and in the Trionyces, or Soft Tortoises, these 

 radiating expansions do not unite throughout ; and even when 

 the four pieces on each side unite together and the odd piece is" joined 

 to those of the first pair, there remains in the middle, between them 

 all and on each side between them and the dorsal buckler, great 

 spaces which are filled up by cartilage only. , 



Vertebrae. The atlas is composed of four pieces. The first two, 

 united above in a slight spinous prominence, after having surrounded 

 the vertebral canal, and each having given backwards its articular 

 apophysis, concur with a third very small one in the formation of a 

 ring for the reception of the condyle of the head : Cuvier calls it a 

 ring, because in the skeleton this fosset is open, and its bottom Blled 

 by a fourth piece, which is a true body of a vertebra without the 

 annular portion, and which, presenting an anterior convex surface in 

 the space here noticed, is articulated behind by a concave surface on 

 the body of the axis. This piece, analogous to what we have already 

 seen in the crocodile, represents, he observes, the odontoid apophysis 

 of the axis of mammals. At their junction, there is besides, attached 

 below, a small bone formed nearly like a patella (rotule). 



The axis and the succeeding vertebras are composed of a nearly 

 rectangular body, carinated below, concave in front, convex behind, 

 and of an annular portion, which remains distinct from the body 

 throughout life, by means of two sutures, is elevated above by a 

 crest in lieu of a spinous apophysis, and whose anterior articular 

 apophyses, placed at first under the posterior portions of the preceding 

 vertebra, raise themselves obliquely to embrace them slightly up to 

 the sixth, and nearly resume their horizontal position in the two 

 succeeding ones. At the anterior angle of each side of the body is a 

 small facet, common to the body and the annular portion. 



The vertebras adhering to the dorsal buckler have their body wide 

 and feebly carinated iu the Marine and Fresh- Water Tortoises : in 

 these last it is even flattened in the anterior ones. It is also wide 

 and with but little convexity in Trionyx, and Chdys has it wide and 

 elevated longitudinally into a small crest. But there are Land- 

 Tortoises (Testudo geometrica and T. rudiata) in which it is exces- 

 sively compressed, and does not even join itself throughout, except 

 by a membranous partition, to the pieces of the middle row of the 

 buckler, these pieces only affording each two narrow lamina;, and 

 descending on each articulation of the two bodies. It is in a fold of ' 

 the lower portion of this membrane, between these vertical laminae, 

 and in a semicanal hollowed at the upper part of the bodies, that the 

 spinal marrow goes. 



In the other sub-genera the pieces of the longitudinal series of the 

 dorsal buckler afford more complete vertical partitions, which form 

 with the bodies a continuous bony canal, the nerves of which go out 

 through holes which remain between the laminae. 



The sacral and caudal vertebra) are each composed of a body, 

 concave before and convex behind, of an annular portion, squarely 

 flattened, and without a spine above, the anterior articular apophyses 

 of which obliquely embrace below the posterior apophyses of the 

 preceding vertebra, aud of two transverse short apophyses, articulated 

 on each side on the suture, which joins the body to the annular ring. 

 Cuvier counted 23 caudal vertebras in Trstudo Gr&ca, T. Jndica, and 

 other Land-Tortoises, and as many as 27 in Teatutlo rodiata. He 



