94 DR. J. E. GRAY ON THE TRIONYCHIDE, [Feb. 23, 
The genus Cycloderma of Peters was instituted to contain all the 
- Cryptopi of Duméril, which had a boneless flexible margin to the 
shield, without paying. any attention to the number of the callosities, 
which are also coexistent with a very differently shaped skull and, 
doubtless, different habits in the animal. 
The skull of this genus is analogous to the skull of the genus Pe- 
lochelys among the naked-footed Trionychide, as the skull of Cy- 
clanosteus resembles that of the more typical Trionychide. 
1. Hepraruyra Frenata. (Skull, figs. 13, 14, 15.) 
Cycloderma frenatum, Peters, Monatsb. 1854, p. 216. 
Cyclanosteus frenatus, Peters, MSS. 1848; Gray, Cat. Shield 
Rept. 64 (1855). 
Cryptopus aubryi, A. Dum. Rev. Zool. 1856, p. 37, t. 20. 
Heptathyra aubryi, Cope, Proc. Acad. N.S. Phil. 1859, p. 296; 
Gray, P. Z. S. 1860, p. 315. 
Hab. Africa: Gaboon (Duméril) ; Mozambique (Pe¢ers). 
The similarity of the descriptions of the bands on the head shows 
that the Cyclanosteus frenatus of Peters and the Oryptopus aubryi 
of Duméril most probably belong to the same species. 
2. HEPTATHYRA LIVINGSTONII. 
Aspidochelys livingstonii, Gray, P. Z. 8. 1860, pp. 6 (pl. xx1.), 
315. 
Hab. Central Africa: River Zambesi. 
This may be the same as the former, not quite so full-grown ; but 
the hinder pair of callosities are oblong and united by their hinder 
edges only, and the colour of the head is not known. Dr. Peters’s 
name, however, and his description of the specimen he had from 
Mozambique show that one of the Heptathyre found on that side of 
Africa has the black streak and cross bands that are characteristic 
of the Gaboon species. 
b. Margin of the dorsal disk flewible, without internal bones ; the 
skull oblong, swollen, convex above; palate concave, with large 
distinct alveolar plates, and a deep central pit before and be- 
hind the internal nostrils. Cyclanosteina. 
CYCLANOSTEUS. 
Cyclanosteus (restricted), Gray, P. Z. S. 1860, 315. 
The face of the skull short, convex, arched in front ; orbits rather 
lateral, shelving ; forehead flat, rhombic, elongate. Palate concave, 
flat behind ; in front with a large, broad, deep concavity behind the 
very large oblong internal nostrils, and a small central, deep, trian- 
gular concavity in front of them. The alveolar plate very broad and 
flat, broader behind, and hooding over and continued far behind the 
internal nostrils. Lower jaw strong, flattened, very broad, simple, 
depressed, and sharp-edged in front, with the hinder half flattened 
out internally into an ovate, rather concave alveolar disk. 
