[Illustration: FIG. 442.--_Midas geoffrei_, Geoffrey's marmoset. Ileo-colic junction and caecum; dried preparation. (Columbia University Museum, No. 197.)] C. CEBIDAE. =1. Ateles= and other howlers have a large caecum, crescentic in shape, narrowed at the apex, separated from the colon by a sharp and deep constriction, opposite the wedge-shaped ileo-colic junction. The ileo-caecal folds are well-developed and symmetrical, two equal vascular folds, and a free intermediate non-vascular reduplication. Types: _Ateles ater_ (Figs. 443-445), _Chrysothrix sciureus_ (Fig. 447) and _Nyctipithecus commersonii_ (Fig. 446). In _Mycetes_ (Figs. 448-450) the pouch is shorter, less curved, with a slight reduction toward the less distinctly pointed apex. [Illustration: FIG. 443.--_Ateles ater_, black-faced coaita. Ileo-colic junction and caecum; dried preparation. (Columbia University Museum, No. 240.)] [Illustration: FIG. 444.--_Ateles ater_, black-faced coaita. Ileo-colic junction and caecum, with ileo-caecal folds. (Columbia University Museum, No. 720.)] [Illustration: FIG. 445.--_Ateles ater_, black-faced coaita. Ileo-colic junction and caecum, with ileo-caecal folds. (Drawn from preparation.) (Columbia University Museum, No. 300.) 1. Ventral vascular ileo-caecal fold. 2. Intermediate non-vascular ileo-caecal fold. 3. Dorsal vascular ileo-caecal fold. ] [Illustration: FIG. 446.--_Nyctipithecus commersonii_, Vitoe monkey. Ileo-colic junction and caecum; dried preparation. (Columbia University Museum, No. 238.)] [Illustration: FIG. 447.--_Chrysothrix sciureus_, Viti monkey. Ileo-colic junction and caecum. (Columbia University Museum, No. 1624.)] [Illustration: FIG. 448.--_Mycetes cavaya_, black howler. Ileo-colic junction and caecum. (Columbia University Museum, No. 1136.)] [Illustration: FIG. 449.--_Mycetes fuscus_, brown howler. Ileo-colic junction and caecum, with ileo-caecal folds; ventral view. (Columbia University Museum, No. 674.) 1. Ventral vascular ileo-caecal fold. 3. Intermediate non-vascular ileo-caecal fold. ] [Illustration: FIG. 450.--Drawn from the same preparation as Fig. 449; dorsal view. 2. Dorsal vascular ileo-caecal fold. 3. Intermediate non-vascular ileo-caecal fold. ] [Illustration: FIG. 451.--_Lagothrix humboldtii_, Humboldt's lagothrix. Ileo-colic junction and caecum. (Columbia University Museum, No. 1511.)] [Illustration: FIG. 452.--_Pithecia satanas_, black saki monkey. Ileo-colic junction and caecum. (Columbia University Museum, No. 641.)] =2. Lagothrix.=--The caecum is very capacious and long, bent at a sharp angle upwards and to the left toward the ileo-colic junction. Type: _Lagothrix humboldtii_ (Fig. 451). =3. Pithecia.=--The caecum resembles in general the type presented by _Ateles_, but is less curved and less reduced and pointed at the termination. Type: _Pithecia satanas_ (Fig. 452).