856 Dll. C. F. SONNTAG ON THE VISCEEAL ANATOMY 



lidfe and Coeoiolestes ohscurits, fewest in Trichostm'us vulpecula, 

 and largest in Pliascolarctos cinereus, but the commonest number 

 is eight. Tliey are most variable in the Polyprotodonts, and the 

 numbers of complete and incomplete ridges are of considerable 

 value for purposes of classification, as shown in the table of 

 formulae given below. 



In all Marsupials the ridges on the anterior part of the hard 

 palate are larger than those on the posterior part, and the pos- 

 terior margin of the palate frequently appears as a well-marked 

 ridge. The spaces between the ridges are occupied by papillae, 

 tubei"cles, or incomplete ridges, and the latter are present in 

 DicUljyliys, Peramehs, Dasyurus, S'arcoj^hilus, and Ccenolestes. The 

 incomplete ridges cross the mid line, and difler from those of 

 many of the higher Mammalia, in which they run from a median 

 raphe to the sides of the palate. 



No Marsupial has a median raphe running the whole length 

 of the palate. 



In a very young pouch specimen of Onychogale lunata the lips 

 are entire, the tongue is excavated to form a bed for the nipple, 

 and the incisive pad and anterior palatal ridges are outlined and 

 hardly elevated ; but the posterior palatal ridges are well-marked. 

 The conditions are such that there is a firm area of contact 

 between the nipple and mouth. In an older pouch specimen of 

 Macropus hennetti the upper lip is cleft, the incisive pad is more 

 prominent, and the anterior palatal ridges are more developed 

 than those of Onychogale ; and in pouch specimens of Macropus 

 giganteus and Phalanger orientalis of still more advanced ages 

 the conditions resemble those of the adult — namely, large incisive 

 pads, strong anterior ridges, and weak posterior ones. 



In animals requiring a firm contact between the mouth and 

 nipples large anterior ridges would be disadvantageous, and they 

 are unnecessary while the diet consists entirely of milk. 



The vestibule and cavum oris communicate posteriorly behind 

 the last molar teeth, and in seA^eral Marsupials the diastemata 

 form anterior communications. 



The Soft Palate is frequently covered with papillae, which are 

 small, but visible to the naked eye. It has no uvula, and thins 

 out posteriorly where it forms the anterior and lateral boundaries 

 of the posterior extremity of the nasal tube ; the orifice of the 

 tube is round and small, or long and pyriform or slit-like. The 

 larynx may be gripped by the tube, or the opening of the tube 

 may overlap its superior aperture. In the mammary foetus the 

 larynx passes into the nasal tube so that the entrance of air is 

 not impeded in suckling *. 



In all Marsupials the oiifices of the Eustachian tubes are 

 within the nose. And these have been figured in my paper on 



* In a maniiscvipt note Garrod states that the soft palate shuts off the glottis 

 from the inouth in Tamandua tetradactijla, and suggests that this arrangement 

 •comes into use when the animal is collecting masses of termites before swallowing. 

 No insects can possibly enter the larynx in consequence, 



