AiiT. 19 A MIOCENE POEPOISE FROM MABYLAND KELLOGG 53 



Measurements of the ribs (in millinieters) — Continued 



Sixth 

 rib 



Left Right 



Greatest length in a 

 straight line 



Greatest breadth of shaft 

 at angle 



Distance between ex- 

 ternal margin of tuber- 

 culum and anterior 

 margin of capitulum 



Greatest thickness of 

 shaft near the middle __ 



Greatest diameter of ar- 

 ticular facet on head of 

 rib 



Greatest diameter of ar- 

 ticular facet on tubercle 

 of rib 



Least breadth of neck 



X 



7.5 

 20. 5 



X 



5. 8 



8. 5 

 4. 8 



X 



7.2 



Seventh 

 rib 



Left Right 



201 + 

 6.5 



26 



X 



5. 8 

 11. 8 



X 

 X 



26. 5 

 5 



12 



4. 9 X 



Eighth 

 rib 



Left Right 



192 + 

 6 



X 



4.4 

 10. 7 



Ninth 

 rib 



Left Right 



183.5 



X 



4 



7. 8 



Tenth 

 rib 



Left Right 



147 + 



X 

 X 



3. 8 



EXPLANATION OF PLATES 



Kentrlodon pcrn'ix. Cat. No. 8060, Division of Vertebrate Palaeontology, 

 United States National Museum. Calvert formation, western shore of Chesa- 

 peake Bay, about one and one-half miles south of Chesapeake Beach, Calvert 

 County, Maryland. Collected by Norman H. Boss, July 5-7, 1913. Cat. No. 

 10670, Division of Vertebrate Palaeontology, United States National Museum. 

 Calvert formation, western shore of Chesapeake Bay, south of Chesapeake 

 Beach, Calvert County, Maryland. Collected by William Palmer, July, 1918. 



The following abbreviations are used on plates 3 to 7. Al., alisphenold ; 

 Ant. n., antorbital notch ; Ap. max., apophysis of maxilla ; Bo., basioccipital ; 

 Bs., basisphenoid ; C, condyle ; Cr. I., lambdoid crest ; Ex. oc, exoccipital ; 

 Fal. pr., falcate process of basioccipital ; Fo. h., hypoglossal foramen ; Fa. inf., 

 infraorbital foramen ; Fo. m., foramen magnum ; Fo. max., maxillary foramen ; 

 Fo. pmx., premaxillary foramen; Fr., frontal; J. inc., jugular incisure; Ju., 

 jugal; La., lachrymal; Max., maxilla; Na., nasal; N. A., respiratory passage; 

 Pa., parietal ; Pmx., premaxilla ; Poc. pr., paroecipital process of exoccipital ; 

 Pt., pterygoid ; 8. oc, supraoccipital ; 8. or. pr., supraorbital process of frontal ; 

 8q., squamosal ; Vo., vomer ; Zyg., zygomatic process of squamosal ; 1, passage 

 for mandibular branch of trigeminal nerve in a cleft on posterior border of 

 alisphenoid ; 2, foramen lacerum posterius. 



Plate 1 



Fig. 1, Skeleton of Kentrlodon pernix. Matrix has been removed to show the 

 position of the various elements. Cat. No. 8060, U.S.N.M. About one-seventh 

 natural size. Left tympanic bulla, about natural size. Fig. 2, Ventral view; 

 Fig. 3, External view ; Fig. 4, Internal view ; Fig. 5, Dorsal view. 



