SYSTEMATIC REVISION 83 



Table VII — Continued. 

 Dissorhophus — Continued : 



6. Twenty-one presacral vertebrae; 2 sacrals; caudals unlcnown, but tail short. 



7. Dorsal vertebra with the neural spines expanded into narrow plates overlying 



the back. Narrow dermal plates overlying and alternating with the neural 

 spines, extending the full width of the body, with an elongate shield in front 

 covering several vertebrae; rugose above. 



8. Ribs double-headed anteriorly. Without posterior prolongation. 



9. Cleithrum present, less expanded and thicker. 



10. Scapula much expanded antero-posteriorly below. 



Alegeinosaurus: 



1-6. Only the middorsal region known. 



7. Dorsal vertebrse with neural spines expanded but not wider than vertebrae. 



Small dermal plates overlying the neural spines directly, and each overlapping 

 the preceding plate, not wider than the vertebras. No enlarged anterior plate. 



8. Ribs double-headed, with a long, slender posterior prolongation from a point 



near the upper end. 



9. Cleithrum present, large as in Cacops. 

 10. Scapula less expanded below. 



Cacops: 



1. Small, not exceeding 500 centimeters in length. 



2. Skull not elongate, elevated, resembling in general proportions that ol Diadectes. 



Orbits large, looking laterally and upward. Otic notch closed, forming a 

 fenestra. 



3. Nares near anterior end, but more lateral in position than in Dissorhophus. 



4. Parasphenoid small, almost vestigial. 



5. One tusk on each prevomer and palatine. Maxillary and mandibular teeth 



small and conical, 22 to 23 in maxillary. 



6. Twenty-one presacral vertebrae, 2 sacrals, 6 pygals, and 15 to 16 chevron- 



bearing caudals. 



7. Dorsal vertebrae with neural spines expanded and wide antero-posteriorly. 



Dermal plates overlying and alternating with the neural spines. Narrow 

 laterally, not greatly wider than the vertebrse; no enlarged anterior plate. 



8. Ribs double-headed anteriorly, without posterior prolongation. 



9. Cleithrum present. Thin and more expanded. 



10. Scapula less expanded below; the interclavicles and clavicles more slender. 



Table VIII. Showing the Characters of the Family Aspidosaurida and the 



Genus Aspidosaurus. 



1. Skull elongate-triangular, nose broadly rounded, resembling Trimerorhachis. 



2. Apices of neural spines expanded into rugose, overlapping plates. 



3. Intercentra without lateral processes for the head of the rib. 



Table IX. Showing the Characters of the Family Trematopsida and the 



Genus Trematops. 



1. Skull triangular, abruptly narrower at orbits. 



2. Orbits in the middle of the skull, looking upwards. 



3. Nares united with elongate antorbital openings. 



4. A single medial opening at extremity of the nose. 



5. Otic notches in form of fenestrae. 



6. Maxillary and mandibular teeth subequal, conical. A single tusk on prevomer 



and two pairs of tusks posteriorly, probably on palatine and maxillary. 



7. Humerus with an ectepicondylar and a short entepicondylar process. Condyles 



well developed. 



8. Femur with a thin ridge on the posterior face. 



9. Twelve tarsal bones. 



10. Phalangeal formula of hind foot 2, 3, 3, 4, 3. Terminal phalanges without claws. 



