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A N A TO \! V AXP I'll V SIOLOGT O F 



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Fig. 4. Glottic, muscles and nerves. 

 — a a', crico-hyoid; the mnsole 

 overlying it in the erico-aryte 

 ii"!ii , 6, superior laryngeal nerve ; 



communicating branch 

 branch to orico- arytenoid; !•'". 

 brauch to crii o hyoid ; c, recur- 

 rent laryngeal; dd', glottic slit; 

 e, point of hyoid bone ; f, tongue. 



is determined by two pairs of muscles situated about 

 the glottis, and controlling its movements. These arc 

 the crico-arytenoid and the crico-hyoid bf Bojanus; to 

 the former is intrusted the opening of the glottic lips, 

 while the latter, acting as a sphincter, serves to close 

 them. Tlte cricoarytenoid (Fig. 4) lies beneath the 

 mucous membrane, superficial to the crico-hyoid, and 

 crossing it nearly at right angles. It arises from the 

 sides of the cricoid cartilage anteriorly, and is inserted 

 into the body and vertical limh of the arytenoid as far 

 as its extreme point. 



The crico-hyoid (Fig. t, a a') arises from the bod) 

 of the hyoid bone anterior to the depression tor the 

 larvnx. its middle resting upon and exterior to the 

 arytenoid cartilage. It is inserted into the cricoid car- 

 tilage at its anterior raphe. The muscles of the two 

 side> approximate each other at their origins, and in- 

 terlace at their insertions, forming an elliptical muscle 

 surrounding the rima glottidis. 



Our opportunities for studying the arrangement of 

 the respiratory muscles in other turtles than Chelydra 

 have been limited to the representatives of two families, 

 Chelonioidse and Emydoidae. 

 Among the Chelonians we have examined but one species, Chelonia mydas, the 

 Green Turtle of the Atlantic Ocean. lt> habits an- entirely aquatic, seeking the 

 land only for the purpose of depositing its eggs. The body is flat, the under 

 surface well covered by the plastron, leaving, however, naked flank spaces, as in the 

 snapper. The union between the plastron and carapace extends from the second 

 to the seventh rib. The inspiratory muscles occupy the Hanks, arising a half 

 inch or more within that part of their boundary which is formed by the plastron. 

 The central tendon exists, and is wide and irregular, and extends the whole length 

 of the muscle. 



The origin of the expiratory muscles is similar to that found in Chelydra ; the 



muscular bellies are shorter, however, and the common tendon broader and longer 

 in accordance with the shape of the turtle. 



The dimensions of the shell are — length, 38 inches; width, 28 inches; elevation, 

 1 'A inches. 



A.mong the Emydoidae we have examined individuals from eighl genera, and 

 find them to present considerable variations in the origin of the anterior belly of the 

 muscle of expiration. And as these differences seem to characterize groups in 

 harmony with the subdivisions of Agassiz, founded on minor differences of form 

 observed in this family, we shall follow his classification in their description. 



The firsl subdivision suggested by this distinguished observer, and styled Xec- 

 temydoidse, is thus characterized : "The bod) is rather flat. The bridge connect- 

 ing the plastron and carapace is wide, but Hat. The hind logs are stouter than the 



