IX PLEURODIRA — PELOMEDUSIDAE 391 



in Madagascar. />'. derbianus in West Africa, from the Gambia 

 to Angola, is the largest species, with a shell nearly one foot in 

 length. 



Pelomediisa. — Skull with a slender parieto-squamosal arch. 

 Meso-plastra small and lateral. Plastron without a hinge. 

 Fore- and hind-limbs with five very short digits and five claws. 

 Top of the head with one pair of shields between the eyes, and 

 with a large interparietal and a pair of parietals behind. 



P. galcata, the only species, occurs in Madagascar and nearly the 

 whole of Africa south of the Sahara, from the Cape to Abyssinia, 

 and in the Sinaitic peninsula. The shell, less than one foot in 

 length, is much depressed and is obtusely keeled ; brown above 

 with black spots ; brownish-yellow below. The short and broad 

 head is coloured like the rest, without ornamentation. In Somali- 

 land this species sleeps hidden on land during the dry seasons, 

 from July to the end of September, and from January to March, 

 and appears at once after the rains have set in. 



Podocnemis. — With a supratemporal roof formed by the 

 junction of the parietal with the quadrato-jugal. Meso-plastra 

 small and lateral. Fore- and hind-limbs broadly webbed, with 

 five and four claws respectively. The fore-arms and the outer 

 edges of the hind-feet with several conspicuous shields, hence the 

 generic name. Head with an interparietal, two parietals, and a 

 narrow unpaired shield between the eyes. The tail is very 

 short. The carapace is flat and broad, strongly serrated on the 

 posterior margin. Chin with one or two short barbels. Several 

 species in South America, chiefly in the basin of the Amazon, and 

 one in Madagascar. * 



P. expansa. — Very common in Tropical South America, east 

 of the Andes. The female, which is much larger than the male, 

 has a shell nearly three feet in length. Olive -brown above 

 with darker patches; yellowish below. With a few yellow 

 spots above and behind the eyes, and on the parietal region. 

 The "Arrau" turtle is of great commercial importance on 

 account of the eggs, which are periodically collected in enormous 

 quantities, chiefly for the oil. This is either eaten, like the 

 eggs themselves, or used for burning in lamps, or as an addition 

 to tar. The turtles are likewise eaten by man and beast. 

 Thousands of the little creatures are snapped up by Jabiru 

 storks, alligators, and fishes ; the adults fall an easy prey 



