24 



EXPLANATION OF PLATES. 



PLATE I. 

 Bones of fishes and tortoises, natural size. 



Fig. 1. Amia whiteavesiana, Cope, anterior vertebra, articular face ; a from above ; b from below. 



Fig. 2. Amia macrospondyla, Cope, anterior vertebra, articular face ; a from above ; 6 from below. 



Fig. 3. Rhineastes rhwas, Cope, dorsal vertebra, articular face; a from above; b the side. 



Fig. 4. Amiurus cancellalus, Cope, dorsal vertebrae, articular face; a from above; 6 from below. 



Fig. 5. Amiurus cancellalus f caudal vertebra, articular face ; a from above ; b from side. 



Fig. 6. Amiurus maconnellii, Cope, dorsal vertebra, articular face ; a from below ; b from side. 



Fig. 7. Amiurus maconnellii f vertebra, articular face ; a from side. 



Fig. S. Trionyx Icucopotamicus, Cope, costal bone from above ; from White Buttes, Dakota, U. S. 



Fig. 9. Trionyx Icucopotamicus, Cope, part of costal bone from above ; typical specimen. 



PLATE II. 

 Right mandibular ramus (lacking posterior part) of the Hemipsalodon grandis, Cope, natural size ; a superior view. 



PLATE III. 



Hemipsalodon grandis, Cope, femora, two-thirds natural size. 

 Fig. 1. Anterior view ; trochanter restored from smaller specimen. 

 Fig. 2. Posterior view ; " " " " " 



Fig. 3- Proximal extremity, end view ; taken from the second and smaller specimen. 

 Fig. 4. Distal end left side ; from specimen No. 1. 



PLATE IV. 



Fig. 1. Chalicolherium bilobatum, Cope, symphyseal part of mandible, the right alveolar ridge wanting, left side ; 



two-thirds natural size; a symphysis, posterior view; 6 from above. 

 Fig. 2. Gcnopus mills, Cope, part of mandibular ramus, with crowns of third and fourth premolars, two-thirds 



natural size, from above. 

 Fig. 3. Oenopus mills, Cope, symphysis and part of left ramus mandibuli, from above ; a from left side. 

 Fig. 4. Cxnopus pumilus, Cope, part of right mandibular ramus from above, natural size. 



PLATE V. 



Fig. 1 . Menodus angustigenis, Cope, posterior four superior molars, three-eighths natural size, from below. 

 Fig. 2. Menodus angustigenis, Cope, mandibular ramus of another individual (also figured on plate vii.), three- 

 eighths natural size. 

 Fig. 3. Menodus sclwynianus, Cope, nasal bones from above, three-eighths natural size ; a the left side ; 6 from 



below. 



PLATE VI. 



Fig. 1. Menodus ? americanus, Leidy '? female ; nasal and part of frontal bone, from above; one-half natural size. 

 Fig. 2. Menodus angustigenis, Cope, left ramus mandibuli, external view ; three-eighths natural size ; a internal 

 side. 



PLATE VII. 



Fig. 1. Menodus angustigenis, Cope, sympyhseal part of right mandibular ramus, from the right side, two-thirds 



natural size ; a from below ; 6 from front. Type of the species. 



Fig. 2. Menodus angustigenis ? Cope, nasal bones and right horn, from the front ; one-half natural size. Type of 



M. si/ceras, Cope. 



PLATE VIII. 



Fig. 1. Menodus ? americanus, Leidy ? female, nasal bones, from the front ; one-half natural size. 



Fig. 2. Menodus 'americanus, specimen represented in fig. 1, left side ; one-half natural size. 



Fig. 3. Same as fig. 2, outline of section of base of left horn. 



Fig. 4. Menodus angustig* t.ls, Cope, (.V. syceras) nasal bones and horn, right side; one-half natural size; external 



view. 

 Fig. 5. Outline of section of base of horn of specimen fig. 4. 



