190 
TEAVELS IN CENTEAL AEEICA. 
like the other fresh- water tortoises^, the back being covered with a 
soft skin_, that is expanded out on the side, so as to form a short 
edged cartilaginous flexible shield. They have only three claws on 
each foot, and the head is covered with a thick soft skin, like the 
body. They are furnished with fleshy lips, which hide the horny 
beak that covers the jaws; the lower lip is bent downwards, and 
the upper ones are dependent over and cover the lower one. 
But I have lately discovered that specimens of the Trionichida 
— that are very like externally, especially in the dry and more or 
less distorted state in which we have them in museums — are in fact 
distinct species, which are easily distinguished by the examination 
of the bones of the head, and especially the form of the chewing 
surface of the jaws. I was induced to soak the head and open 
the jaws of the specimen which I received from you, and those 
which we had from Mr. Burton from the Lower Nile, and also the 
specimens which we purchased of M. Du Chaillu from the Gaboon, 
under the name of Aspidonectes Aspilus (Cope), and I was much 
pleased to observe that the specimens from the Upper Nile or 
Khartoum, differing entirely in the form of the masticating surface 
of the jaws from both the specimens of the Lower Nile and the 
Gaboon : the skull and masticating surfaces of the two latter were 
exactly alike, and are the well-known Tijrsa Nilotica, while the 
animals which you sent from Khartoum were so different that I have 
considered them as the types of a new species, forming a distinct 
genus in the family, which I have named Fordia Africana, after Mr. 
Ford, so well known for his beautiful lithographic figures of reptiles, 
fishes, corals, and other animals. 
When the differences in the form of the masticating surface 
of the jaws were observed, and the attention was called to the 
difference that existed between’ the two mud tortoises, it was easily 
