Cerebral hemispheres larger and well convoluted. Facial portion of skull produced into a long, tapering, tubular rostrum, at the end of which the anterior nares are situated. Rami of mandible slender, styliform. Opening of mouth small, and placed below the extremity of the rostrum. No teeth or laterally placed horny plates, though the palate and tongue are furnished with spines. Tongue very long, vermiform, slender, and protractile. Lining membrane of small intestine villous, but without transverse folds. Feet not webbed, but with long strong claws fitted for scratching and burrowing. The hinder feet with the ends of the toes turned outwards and backwards in the ordinary position of the animal when on the ground. Tail very short. Acetabulum with a large perforation, as in Birds. Calcaneal spur and gland of the male much smaller than in _Ornithorhynchus_. Fur intermixed with strong, sharp-pointed spines. Terrestrial and fossorial in habits, feeding exclusively on ants, and recalling in the structure of the mouth and various other parts, relating to their peculiar mode of life the true Anteaters of the order Edentata. The Echidnas or Spiny Anteaters constitute a family which appears in some respects to be less specialised than the _Ornithorhynchidæ_. According to Mr. O. Thomas, all the living forms may be included in two species, which, with some hesitation, are referred to two genera—_Echidna_ and _Proechidna_ (_Acanthoglossus_). _Echidna._[35]—In _Echidna_ there are five toes, all of which are provided with claws, those of the fore foot being broad, slightly curved, and directed forwards, while the posterior ones are slender, more curved, and inclined outwardly. The beak is about as long as the rest of the head, and either nearly straight, or slightly curved upwards, while the palate is comparatively wide, and but slightly vaulted. The number of the vertebræ is C 7, D 16, L 3, S 3, Ca 12. The one existing representative of the genus (_E. aculeata_) occurs in New Guinea, Tasmania, and Australia. So much variation is displayed by this animal, that it has been divided into several species, but the latest researches tend to show that these variations cannot be regarded as indicating more than races, of which there are three well-marked types. The first race, or variety, has been termed the Port Moresby Echidna, and is only known from that Papuan locality. It is distinguished from the typical form by its smaller size, by the shorter spines on the back, which admit of the fur being seen, and by the more spinous covering of the head, belly, and limbs, as well as by the lighter skull and relatively larger beak.