ANOMODONTIA 105 



The skull is of most extraordinary form. The lace is turned 

 downward, leavin<ij the nostrils hifi;h up, in front of the eyes. The 

 jaws were doubtless covered with a horny shield, like that of the 

 turtles, having a cutting edge. There is a single pair of elongated 

 canine teeth, possibly a sexual character. The lower jaws are 

 heavy and stout, and Watson has said that the animal doubtless 

 had the ability to open its mouth very widely. The quadrate, the 

 bone with which the lower jaws articulate, is lirmly fixed to the 

 skull, and there is a single opening on the side of the skull poste- 

 riorly, a character common to all the Therapsida. 



The vertebrae are stout, and they have stout spines. The tail 

 is remarkably short, stout, and stumpy; it could have been of no 

 use whatever in the water for propulsion or even for steering. The 

 front legs are short and stout; the forearm bones are short, sug- 

 gesting either swimming or digging habits, and the foot is short and 

 broad. The pelvis or hip bones are massive and were very firmly 

 connected with the backbone by the aid of six vertebrae, a very 

 unusual number in reptiles. The hind legs, as figured, show no 

 indications whatever of aquatic adaptation, unless possibly the 

 very slight shortening of the shin may be so construed. Watson 

 believes that the bones of the pelvis, indicate, aside from its strong 

 union with the backbones, strong swimming powers, but of this 

 again the present writer is very skeptical. The very strong ischia 

 and the flatness of the pelvis are both characters found among 

 American Permian reptiles, which do not show otherwise the 

 slightest indications of water habits. 



If then Lystrosaurus was a powerful swimmer, as has been 

 maintained, it is very evident that the hind legs must have been 

 used as the seals or sea-otters use them, to propel and to guide; 

 but they in nowise resemble the legs of these swimming mammals. 

 It seems altogether more reasonable to suppose that Lystrosaurus 

 lived in the marshes, feeding upon vegetable food obtained by aid 

 of its strong jaws and tusks--if the tusks were possessed by both 

 sexes; and that the position of the nostrils may be ascribed to 

 causes like those which brought about their recession in the Phyto- 

 sauria, and not to strictly aquatic habits. . Possibly the animal had 

 habits somewhat similar to those of the hippopotamus; that it was 



