270 



AMERICAN TESTUDINATA. 



Part II. 



SECTION VII. 



MUSCLES. 



The ordinal characters of the Turtles, as far as the muscles' are concerned, 

 are particularly obvious in the muscles of the neck and in those of the region 

 of the trunk. That bulk of muscles which in Ophidians and Saurians lies above 

 and below the vertebral column and the ribs has almost entirely disappeared, 

 owing to the immovability of the trunk.^ There exist only two muscles along 

 the back of the Turtle, and even these disappear in that family, which is char- 

 acteristic of the highest development of the order, in the land Turtles. These 

 muscles are, a musculus longissimus dorsi and a M. retrahens capitis collique, both 

 orieinatins from the dorsal column or its neighborhood, and attached to the neck 

 or to the head ; so that, properly speaking, even these are more muscles of the 

 neck than of the trunk. 



The musculus longissimus dorsi ^ runs along the back on both sides of the 

 vertebrre, between the ossified corium and the ribs. It originates from about 

 the eighth or ninth to the fourth or third rib and the dorsal shield of that 

 neighborhood, and is attached to the last or to the two last vertebrae of the neck. 

 It is very large and powerful in the family of the Snapping-Turtles, (Chelydroidag,) 

 the arches through which it passes being here high and broad. This passage is 

 much narrower in the family of the Emydoidaj, and the muscle also much weaker; 

 in Cistudo virginea, the highest of the Emydoidas and the nearest to the land 

 Turtles, we see it developed only in the anterior part of the trunk, until in the 

 land Turtles it disappears entirely. Even the arches through which it passes in 

 other Turtles disappear in consequence of the resorption of the ribs which takes 



* For further details i-espectiiig the muscular 

 system, see Bojanus, Anatome Testudinis Europjeie, 

 Vilnse, 1819-21, 1st vol. For a comprehensive 

 abstract of what is now known respecting the mos- 

 cular apparatus of all Turtles, see the valuable 

 work of Stannius, Zootomie der Wirbelthiere, 2d 

 edit., Berlin, 1856. 



^ A distinct muscular layer above the ribs, and 

 distinct museuli intercostales, are only to be found 

 in very young Turtles, in embryos, or in specimens 

 recently hatched. I have seen these muscles most 

 distinctly in the young Chelydra serpentina and in 



Trionyx ferox. See also Rathke, (R.,) Ueber die 

 Entwickelung der SchildkriJten, p. 155. 



° In Emys serrata, Lesueurii, and geographica, 

 this muscle is much smaller than in E. Europoea, as it 

 has been described by Bojanus. In Emys ctmcentrica, 

 it is the same as in the European species. But in 

 Chelydra serpentina this muscle is very powerful, 

 and the arches, near the dorsal column, through which 

 it passes, are very large and high. In Chelonia 

 Mydas, it is small. In Cistudo, we find it only 

 in the anterior part of the dorsal column, and in 

 Testudo there is no trace of it. 



