The Apishapa quadrangle, the geographic relations of which are shown by Plate IV, is situated on the plains south of Arkansas River, in Colorado, about 24 miles east of the mountain front. The geology of the Pueblo, Walsenburg, Spanish Peaks, and Elmoro quadrangles, adjoining it on the northwest, west, southwest, and south, respectively, has been described in folios of the Geologic Atlas. G. K. Gilbert, assisted by F. P. Gulliver and G. W. Stose, took up the survey of the Apishapa area in 1894. The Apishapa folio was completed by Stose and was issued in 1913. The rocks to be described in this paper were collected by Gilbert and his assistants, the present writer never having visited the area. The following description of the occurrence of the has been kindly furnished by Mr. Stose.