88 DR. J. E. GRAY ON THE TRIONYCHID. [Feb. 23, 
head flat. Eyes submedial. Upper jaw with a broad concave alve- 
olar plate of nearly equal width in all parts. The lower jaw with a 
sharp edge, with only very slight indications of a flattened alveolar 
edge on the hinder part of the inner side; the front of the jaw 
shelving forwards, and with a large concavity on the upper surface 
behind the edges. The palate flat behind, with a broad concavity 
in front of the internal nostrils, which is continued behind on both 
sides of them. The internal nostrils large, oblong, far back, nearly 
in a line with the front of the zygomatic arches, and with a large 
deep concavity, separated by a central longitudinal ridge, behind 
each of them. The nostrils large, rounded, with an internal lobe 
on the inner edge (see Wagler, N. Syst. Amph. t. 2. f. 19). 
The skull of this genus is at once known from those of the genus 
Trionyz, by the nose being elongated, shelving, and not rounded, and 
by the form of the palate. The skull of a young specimen from the 
Nile is figured in the ‘Cat. of Shield Reptiles,’ t. 42. f. 2. 
Tyrse nitoTica, Gray, Cat. Tort. B. M. 48. 
Trionyzx niloticus, Gray, Syn. Rept. 48 ; Cat. Shield Rept. 68. 
Testudo triunguis, Forsk. 
Trionyx egyptiacus, Geoff. Egyp. 
Gymnopus egyptiacus, Dum. & Bibr. 
Trionyx labrosus, Bell, Test. 
Aspidonectes egyptiacus, Fitz. 
Aspidonectes aspilus, Cope, Proc. Acad. Nat. Sci. Philad. 1859, 
p- 295 (adult). 
Hab. Africa, North and West: Fernando Vas River( Cope); Sierra 
Leone (Bell). 
The young specimens have the head, limbs, and edge of the shield 
dusky, with round white spots. 
The very large specimen of Trionyx from Western Africa, obtained 
from M. Du Chaillu, agrees with Mr. Cope’s description of Aspido- 
nectes aspilus; I can see no difference between it and the half-grown 
specimens of Trionyx niloticus from Egypt in the British Museum. 
In the two Egyptian specimens the hinder callosities are separated 
from the lateral ones, and the hinder part of the inner edge of the 
lateral callosities is regularly rounded. In the very large adult 
West African specimen the front edge of the hinder callosities is 
furnished with a process that fits into a notch in the hinder edge of 
the lateral callosities; and the inner edge of the lateral callosities 
is straight, and then bent off at an acute angle at the hinder part. 
But this is only a difference depending on age; for-a more adult 
specimen collected at Chartoum by Mr. Petherick, in the British 
Museum, has the lobe and notch in the hinder edge of the lateral 
callosity well marked, and the hinder part of the immer edge of the 
lateral callosities approaches more nearly the form of the callosity in 
the larger and more adult West-African specimen. 
There is a large skull and other bones of a species of the genus in 
the Museum of the College of Surgeons, which was presented by 
Captain Sir Everard Home. The locality of the species is not 
LS 
