148 



Genui' TRIONYX, Geoff. 



Trionyx, Geoffroy, 1809, 85, 84; Gray, 1855, So, 64; Boulenger, 1889, 

 8i, 242. 



PJastron little developed behind, leaving the hinder limbs and tail 

 -completely exposed ; with not more than 5 callosities No marginal 

 bones in the border of the carapace. Jaws strong. 



A genus embracing about 15 species, residents in the rivers of North 

 America, Asia and Africa. 



A. Nostril circular, having uo papilla projecting into it from the 

 septum. (Amyda, Agassiz.) 2. muticus, p. 143. 



AA. Nostril crescent-shaped, having a papilla projecting into it from 

 the septum. (Aspidonectes, Agassiz.) 

 a. Uuder side of feet white, not mottled with brown. 



T. agassizii, p. 144. 

 aa. Under side of feet mottled with white and brown. 



T. spinifenis, p. 146. 



Trionyx muticus, LeS. 

 Spineless Soft-Shelled Turtle 



Trionyx muticus, LeSueur, 1827, 86, 263, pi. 7; Holbrook, 1842, o4-, 

 ii, 19. pi. 2; Gray, 1855, So, i, 69; Boulenger, 1889, 84, 260. 



Amyda midica, Agassiz, 1857, 4. i» 399 ; Aspidonedes muticus, Baur, 

 1888,^^, 1122. 



Head long, low, and pointed in front, descending rapidly in front of 

 the eyes. Skull, from the eyes forward, drawn out, the margins of the 

 upper and the lower jaw being concave outwardly. The horny upper 

 jaw with a cutting edge, which is deepest forward and iiluntly toothed 

 posteriorly. Lower jaw also with a sharp edge, and both jaws furnished 

 with an alveolar surface, the leathery snout ending obliquely, so that 

 the nostrils are somewhat under the tip. The nostrils are circular, there 

 being no papilla projecting into them from the septum. 



Body flat and oval. No trace of keel along the middle of the back ; 

 often a depression instead. No spines along the anterior border of the 

 carapace, nor any tubercles anywhere. Callosities well developed on the 

 plastron of the adults, especially of the males. 



The color above is brownish, olive, or bluish-gray. In the young there 

 are some blotches of dark brown. On the margins of the carapace, lat- 

 erally and posteriorly, is a band of yellow, bordered internally with 

 black. These bands are likely to disappear later in life. Head with a 

 white stripe, margined with black, from the eye over the ear and then 

 descending on the neck. Head and neck below the level of the edge of 

 the upper lip white, without any mottling. Under surface of the feet 

 white or bluish-gray ; never mottled as in T. spinifenis. 



