lOlU.] " Marsupiar Characters of Monotremes. 157 



(5) Diaphragm perfectly normal (Beddard, /. c, p. 109). 



(6) Stylomastoid foramen for exit of facial nerve piercing the mastoid 

 process inferiorly at its' external angle. This foramen is constant in mammals 

 (Weber, 1904, p. 53). 



(7) Seven cervical vertebriie, as in mammals. 



(8) 19 or 20 dorso-lumbar vertebra? (0.), as in primitive mammals. 



(9) Large pectineal tubercle on pubis, as in many primitive mammals. 



(10) Auditory ossicles of adult not differing in essentials from those of 

 other mammals (Doran, 1879). 



(11) Ontogeny of the auditory ossicles also of mammalian type: c. g., 

 cartilaginous "Anlage" of malleus continuous with Meckel's cartilage 

 (Gaupp, 1908). 



(12) Tympanic membrane with middle layer, or membrana propria as 

 in typical mammals {rf. p. 127 above, Denker, 1901). 



Characters suggesting Affinity with the Marsupials. 



Both groups possess the following characters in common: 



(1) Typical mammalian hairs, formed in identically the same manner 

 (Spencer and Sweet, 1899) the differences being in detail only (see p. 146). 



(2) Acinose and tubular glands. 



(3) Milk glands which, while differing from those of Marsupials in 

 mode of development, are regarded as derivatives of a single type (Weber, 

 1904, p. 31). 



(4) The glandular mammary area in Monotremes is homologized by 

 Gegenbaur, Ruge and Weber (1904, pp. 31, 34) with the teats of Marsupials, 

 while the pouch is probably homologous in the two groups. 



(5) The cartilages of the larynx are homologous and strikingly similar 

 in the two groups; the cricoid cartilages in Echidna realize the ancestral 

 condition of the Marsupials since they remain unconnected dorsally (Weber, 

 1904, p. 218). 



(6) Epipubic bones, preformed in cartilage. 



(7) Three auditory ossicles of similar embryonic history. Although in 

 the Monotremes there are some secondary fusions and modifications, yet 

 there is a general resemblance between the ossicula in the Monotremes and 

 Diprotodonts, which is especially noticeable in the similar elongation of 

 the anterior process of the malleus (c/. Doran, 1879). 



(8) Optic foramen not separated from foramen lacerum anterius 

 (sphenorbital), a reptilian inheritance (c/. Parker, 1886, p. 271). 



(9) In the foetal Marsupials (at least in the Diprotodont genera Tricho- 



