[Figs. 311]-[315] illustrate the structures in representative Teleosts.
Among the higher forms this type of ileo-colic junction is encountered in the simple alimentary canal of many Amphibians ([Figs. 318]-[320]). Among Reptiles it is found in certain lizards, as in Heloderma suspectum, the gila monster ([Fig. 322]). This animal lives almost entirely upon bird’s eggs, and its simple and reduced ileo-colic junction contrasts strongly with the highly developed and complicated cæcal apparatus of the phytophagous lizards, as Iguana ([Figs. 326]-[330]), affording one of the most striking illustrations of the effect which the character of the food habitually taken has on the structure of the alimentary canal in forms otherwise closely allied.
The same type of ileo-colic junction, as a reduction form, occurs in the arctoid group of Carnivora among Mammalia (cf. [p. 212]).
2. Differentiation in caliber of large and small intestine. Funnel-shaped ileo-colic transition.
This type, compared with the preceding, is characterized ([Fig. 465], I, 2) by the greatly increased caliber of the large intestine, resulting in a funnel-shaped transition between mid- and hindgut, the small intestine continuing into the colon at the apex of the funnel.
Examples of this type are presented by several Edentates, Myrmecophaga jubata, the great ant-eater ([Fig. 356]), and Cholœpus didactylus, the two-toed sloth ([Fig. 357]).
3. Abrupt demarcation of small and large intestine with caliber differentiation ([Fig. 465], I, 3).
The small intestine is still central at the ileo-colic junction, i. e., the axis of its lumen is continuous with the central axis of the colic lumen. In place of the gradual funnel-shaped transition of the preceding type the demarcation is abrupt.
An example of this form is furnished by another Edentate, Tatusia peba, the nine-banded armadillo ([Fig. 358]).
Among reptiles a similar well-marked ileo-colic transition is encountered in Alligator mississippiensis ([Fig. 321]).