SUB-ORDER 1. AGLOSSA.–The two diagnostic peculiarities of the few members of this group are: first, the absence of a tongue; secondly, the union of the Eustachian tubes into one median pharyngeal opening in the posterior portion of the palate. [Illustration: FIG. 28.–Map showing distribution of Aglossa. _Hymenochirus_ to be added in Equatorial Africa.] The pharyngeal opening and the tubes themselves are wide, the tympanic cavities are present, but the tympanic discs are not distinct from the rest of the skin. The fronto-parietal bones are fused into one mass, a rare feature in the Anura. The nasals are large. _Pipa_ and _Hymenochirus_ have no teeth, _Xenopus_ has teeth on the upper jaw. The vertebrae are opisthocoelous and typically epichordal in their development; the second, third, and fourth carry long ribs, which in old specimens fuse with the supporting diapophyses. The sacral diapophyses are enormously dilated, and the sacrum is fused with the os coccygeum. The serial number of the sacral vertebrae exhibits a most interesting gradation. In _Xenopus_ the ilium is carried by the diapophyses of the 9th, in _Pipa_ the 9th and 8th, in _Hymenochirus_ the 7th and 6th. In these cases the two diapophyses of each side are fused together into a single broad blade, and their original duplicity is indicated only by the {144}holes for the spinal nerves. _Hymenochirus_ has consequently only 5 presacral vertebrae, the vertebral column being shortened to the greatest extent known amongst Vertebrata. For further information see p. 22. The ilia are much broadened vertically, and are firmly attached to the sacrum. The shoulder-girdle is sometimes described as of the arciferous type, but this is quite unjustifiable. The epicoracoid cartilages do not overlap each other, but meet, and partly fuse in the middle line. The three genera exhibit some differences. In _Pipa_ and _Hymenochirus_ the bony portions of the coracoids are much expanded dorsally, and there is a considerable amount of epicoracoid cartilage, that of the precoracoid bars extending backwards as a broad-based and blunt omosternum. _Xenopus_ is devoid of an omosternum, and the configuration of the whole apparatus is more slender. The metasternum of _Xenopus_ and _Hymenochirus_ broadens out laterally. _Hymenochirus_ greatly resembles _Breviceps_, a genus of Engystomatinae, in the relative position and size of the various parts of the shoulder-girdle and sternum. The tibio-fibula of _Hymenochirus_ has a wing-like expansion of thin bone on each side, forming a deep groove on the outer aspect. The astragalus and calcaneum are united by a similar bony expansion with wing-like projections.