62 DR. J. E. GRAY ON THE TRIONYCHTD^E. [Jan. 7, 



alveolar margin concave, much wider in front, narrower on the sides, 

 and becoming narrower at the end. Length to condyle 1^ inch ; 

 breadth at ears § inch. 



** Skull very slender in front ; nose-hole longer than broad ; lower 

 jaw contracted in the front of the side margin. 



2. Callinia microcephala. (Fig. 11, p. 63.) 



Potamochelysl microcephala, Gray, P. Z. S. 1864, p. 87. 



Callinia microcephala, Gray, P. Z. S. 1869, p. 220; Suppl. Cat. 

 Sh. Rept. p. 108. 



Hab. Borneo, Sarawak. 



Skull slender, rather thin ; nose much attenuated and acute in 

 front, not quite as long as the diameter of the orbit ; nose-hole very 

 large, with the nasal bones acute and projecting into the upper sur- 

 face ; space between the side of the nose-hole and the orbit very 

 small, not a quarter the size of the diameter of the large orbit ; fore- 

 head lozenge-shaped, elongate ; palatine surface nearly flat, with a 

 wide, rather shallow groove, which is as wide as the front of the 

 large internal nostrils, and continued as a line along their outer sides. 

 Lower jaw very slight and slender, rather produced in front, where 

 the rami are united, about one third the length of the front part of 

 the jaw to the condyle ; alveolar surface narrow, acute in front, 

 which is concave internally and on the sides, where the jaws are 

 compressed. Length of skull l^inch ; breadth ^inch. 



The skull is something like Tyrse ; but the nose is shorter, nose- 

 hole much larger and extending up the sides of the face ; anterioi 

 central groove not so large behind. 



The skull is very like Callinia spinifera, but is much more slender, 

 and more sharp and attenuated in front ; and the lower jaw is also 

 much more attenuated and rather contracted on the front of the sides ; 

 the nose-hole is narrower and more elongate. 



10. Amyda. 



Amyda, Gray, Suppl. Cat. Sh. Rept. p. 95. 



This is one of the few Mud-tortoises that I have not seen. 

 Agassiz says, "The lower jaw is sharp-edged all round." 



1. Amyda mutica. 



Trionyx muticus, Lesueur, Mem. Mus. xv. p. 237, fig. 7 ; Hol- 

 brook, Herp. N. Amer. ii. p. 19, t. 2 ; Gray, Syn. Rept. p. 46 ; Cat. 

 Sh. Rept. p. 69. 



Gymnopus muticus, Dum. et Bibr. Erpet. Gen. ii. p. 482. 



Amyda mutica, Agassiz, Contrib. p. 390, t. 6. figs. 6, 7 (very 

 young) ; Gray, Suppl. Cat. Sh. Rept. p. 95. 



Hab. N. America (Lesueur). 



11. Tyrse. 



Tyrse, Gray, P. Z. S. 1864, p. 87 ; Suppl. Cat. Sh. Rept. p. 107 

 (skull) ; Gray, Cat. Sh. Rept. t. 42. f. 2 ; Tortoises, Terrapins, and 

 Turtles, tab. (skull and skeleton). 



