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Show 1892.] POSITION OF NOTORYCTES TYPHLOPS. 369 his own suggestion as to the incisor nature of the so-called canines were correct, the creature would of course be an aberrant Polyprotodont : but this absence of true canines would not affect its Marsupial affinities, and would not in any way bring it nearer to the Monotremata, because we know several genera of true Marsupials which have no canine teeth. I have shown that Notoryctes is aberrantly polyprotodont in spite of the presence of canine teeth. The enumeration of the following characters of Notoryctes will perhaps help to settle its affinities:- A. Characters which prove Notoryctes to be a member of the Metatheria. 1. Possession of an apparently permanent marsupium, with two localized mammae and nipples. 2. Well-developed inner angular process of the mandible. B. Characters of Notoryctes which occur also in some Metatheria. 1. Large movable chevron-bones in the caudal vertebrae: Ma-cropus, Dasyurus, &c. 2. Acromion much elongated and curved over the humerus : Dasyurus. 3. Large osseous bulla auris: Peragalea (Macrotis) lagotis, Perameles, Dasyurus ursinus, Phascoloyale. 4. Very rudimentary marsupial bones: Thylacinus. 5. Opening of marsupium directed backwards : Perameles. 6. Presence of a prehallnx, i.e. the " sesamoid " bone attached by ligament to the entocuneiform, described by Stirling, p. 180, pi. viii. fig. 8 s. Occurs also in Didelphys. 7. Presence of an osseous patella : Perameles. 8. Clavicles not directly attached to sternum, but by intervention of ligaments. A precoracoid unossified segment is usually present in Metatheria. 9. Presence of a " meso-scapular segment." Usual in Metatheria. C. Characters of Notoryctes, not found in recent Marsupials : see numbers 1, 2, 4, 6, 7, 8 of Edentate resemblances (p. 362); further, in opposition to Monotremata, the prepenial, extrapelvic, not abdominal position of the testicles combined with the absence o of a scrotum. Lastly, ? incisors. D. Character unique in Notoryctes : fusion of the cuboid with the ectocuneiform of the foot. It so happens that the characters enumerated above do not permit any decided conclusion, except that Notoryctes might be looked upon as a " very old and generalized form " which has some characters in common with almost every other existing Marsupial family. But this not unfrequent mode of cutting the knot of the difficulty of settling the systematic position of a peculiar nature will hardly be advisable in the face of the highly specialized structure of Notoryctes. W e have to make further inquiries. Notoryctes is fossorial to an |
