368 PROCEEDINGS OF THE ACADEMY OF [June, 



uterus. The zoue measured from outer edge to outer edge about 

 5 centimeters (2 inches), the average breadth of the rim of the 

 zone 1.2 centimeters (.5 inch), the breadth of the space between 

 the inner edges of the zone and destitute of villi 2.5 centimeters 

 (1 inch). The placenta in the six-banded armadillo is not, how- 

 ever, a zonular one in the sense in which that word is used by- 

 anatomists. It does not surround the chorion as a broad baud, the 

 poles of the latter being bare as in the " diffuse " non-deciduate 

 placenta of the pig ; nor as a narrow one as in the " zonular " 

 deciduous placenta of the Carnivora, etc. It should be regarded 

 morphologically rather as a discoidal placenta, the central portion 

 of the disk — ihat is, the part of the chorion lying within the inner 

 edges of the rims of the villous zoue — presenting, however, no 

 villi. The placenta in Dasypus sexcinctiis being therefore ring- 

 shaped, rather than discoid in form, if it be permitted to introduce 

 a new name in anatomical nomenclature, it might be described as 

 a non-deciduate cricoid placenta." The villi, measuring on an 

 average 20 mm. (.8 inch), were not simple as in the Pachy- 

 dermata, Camelidte and Tragulid^e, but compound as in Man. 

 They presented a beautiful arborescent appearance (Plate XVIII, 

 fig. 3), the terminal twigs ending in bulbous or rounded extremi- 

 ties (fig. 4). As is well known, Von Baer,'' Eschricht,^' the elder 

 Milne -Edwards," Huxley," and in recent times Haeckel,^' advo- 

 cated classifying the monodelphous mammalia according to the 

 character of the placentation. It is obvious, however, as shown 

 by the summary given below, that on such a basis the diff^ercnt 

 members of the Edentata would be associated with mammals with 

 which they have no natural affinities, just as, according to such 

 classification, totally different animals like the Hyrax, Elephant, 

 and Carnivora are associated, and which constitutes one of the most 

 important objections that have been urged to the acceptance of 

 such classification. 



If KpiKo?, a ring. 



" Untermclmnrjen uber die Gefassverbindung zwischen, Mutter und 

 Frucht, 1828. 



^^ De Orrjunis qum Respiratione et Nutritioni Fcetus Mammalium inser- 

 viunt, 1837. 



" Annales des Sciences Natxirelles, Serie 3, Tome I, 1844, p. 65. 



^* Elernents of Comparative Anatomy, p. 112. 



^^ Anthropocjenie, 1891, S. 591. 



