K E S 1' 1 K A T J N I N T II E C 11 E L O XI .V . 1 ", 



fore legs, and provided with a broad web, extending beyond the articulation of the 

 nail joint. The representatives of this group arc the largest, and must, aquatic of 

 the whole family." Of the genera included in this sub-family we have observed 

 four: Ptychemys, Graptemys, Malacoclemmys and Chrysemys. 



Fig. 5. 



Fig. 5. Diagram of carapace of turtle, showing with the dotted lines the two principal types of origin of the 

 expiratory muscle. The left side of the diagram shows the line of origin in the most aquatic species. The 

 right side that of the most terrestrial. The numbers indicate the ribs. 



Ptychemys rugosa, Ag. — The inspiratory muscles are found in the flanks as usual, 

 but they have no central tendon, a simple line or raphe marking the junction of 

 the converging fibres. 



The anterior belly of the expiratory muscles arises from the vertebral margin of 

 the fourth and fifth intercostal spaces and from the surface of the fourth rib near 

 its posterior edge for a distance one-third its length. From this right-angular 

 origin the fibres diverge, expanding over the upper and anterior surface of the 

 lung, to join the common tendon at the anterior and inferior pulmonary margin. 

 The fibres extending back on the under surface of the lung, as indicated by the 

 dotted lines (Fig. 3, h), are numerous and large in this species, and seem almost to 

 foreshadow the muscular separation between the thoracic and abdominal viscera 

 in higher vertebrates. 



The posterior belly in its origin presents no variation from that of the Snapper. 

 Its outermost fibres, however, are much developed, forming a muscular band which 

 reaches forwards nearly as far as the anterior junction of the carapace and plastron. 

 The dimensions of this turtle are — length, 11 inches; width, 8^-, inches; and 

 elevation, 5 inches. 



Ptychemys mobiliensis. — Shell measurements. Length, 13J| inches; width, 9 T * ? 

 inches; elevation, 6-L inches. The general shape and appearance of this turtle 

 resembles P. rugosa. The anterior and posterior extremities of the bridge con- 



