In the purely carnivorous Marsupials, comprising the family of the _Dasyuridae_, the reduction of the caecal apparatus, foreshadowed by the appearance of the distal rudimentary segment as a vermiform appendix in the wombats, has been carried to the complete elimination of the pouch. The ileo-colic junction in these animals is simple, marked externally by a circular constriction and internally by an annular valve. The colon forms a very short terminal segment of the alimentary canal. The parts are shown in Fig. 355 in a typical representative of the family, _Dasyurus viverinus_, the Tasmanian devil. [Illustration: FIG. 355.--_Dasyurus viverinus_, dasyurus, Tasmanian devil. Intestinal canal. Ileo-colic junction. (Columbia University Museum, No. 1463.)] The structural modifications encountered in the digestive tract of these carnivorous Marsupials can properly be regarded as the result of their habitual diet, and we will meet with analogous and identical examples of caecal reduction in the typical Carnivores among the placental mammals (cf. p. 212). III. Subclass: Monodelphia. III. Order: Edentata. In all probability the Sloths, Ant-eaters and Armadillos composing this order represent a highly specialized remnant of an ancient group now largely extinct. In respect to the ileo-colic junction the Edentates may be arranged in two groups which offer, within the limited number of existing species, a very complete transitional series. I. SYMMETRICAL TYPE OF ILEO-COLIC JUNCTION. 1. _Differentiation in caliber, with direct funnel-like transition of small into large intestine. No caecum._ Beyond the ileo-colic junction the caliber of the large intestine increases gradually. The terminal ileum is thus implanted into the apex of a funnel formed by the proximal segment of the colon. Examples of this type are furnished by _Myrmecophaga jubata_, the great ant-eater (Fig. 356), and by _Choloepus didactylus_, the two-toed sloth (Fig. 357). [Illustration: FIG. 356.--_Myrmecophaga jubata_, great ant-eater. Ileo-colic junction. (Columbia University Museum, No. 1519.)] [Illustration: FIG. 357.--_Choloepus didactylus_, two-toed sloth. Ileo-colic junction. (Columbia University Museum, No. 714.)] 2. _Abrupt demarcation of small and large intestine, with median transition of ileum._ The caliber of the intestine enlarges rapidly immediately beyond the ileo-colic junction. This form is derived from the preceding by the substitution of the abrupt ileo-colic transition for the gradual funnel-shaped development of the large intestine. The type is illustrated by _Tatusia novemcincta_, the nine-banded armadillo (Fig. 358), and is also found in two other armadillos, _Tolypeutes_ and _Xenurus_. [Illustration: FIG. 358.--_Tatusia novemcincta_, nine-banded armadillo. Ileo-colic junction. (Columbia University Museum, No. 176.)]