No. 566] EDAPHOSAURUS CRUCIGER 



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mainder is based upon careful measurements from a 

 single specimen. So far from being a carnivorous, rap- 

 torial animal similar to Dimetrodon, Edaphosaurus was 

 harmless, molluscivorous or insectivorous with possibly 

 some ability to masticate vegetable matter. The edges 

 of the jaws were lined with sharp conical teeth and upon 

 the palate and the dentary bones were strong plates sup- 

 porting numerous blunt, conical teeth. The head in all 

 specimens recovered seems rather small for the size of 

 the body and in this is peculiar in the Permo-Carbonif- 

 erous reptilian fauna, in which the reverse is the rule. 

 The shape of the head in the restoration is taken from the 

 nearly perfect and undistorted skull in the museum of the 

 University of Chicago. The elevated dorsal spines begin 

 with the third vertebrae and speedily reach a considerable 

 height. The lateral projections are elongate at the base 

 of the spine but above the middle are reduced to mere 

 nodules irregularly arranged. The author is not in ac- 

 cord with the suggestion made by Jaekel and Abel that 

 the spines were separate, and can see no reason for the 

 suggestion made by the former that the spines were mov- 

 able. The strongly interlocking zygapophyses render such 

 an idea impossible to any one familiar with the skeleton. 

 Nor does the author believe that the spines were of any 

 use to the creature as offensive or defensive weapons; 

 rather, as he has frequently expressed himself, he believes 

 that they were in the nature of excessive growths which 

 may have had their inception and impetus in some useful 

 function, but grew beyond that use as the animal became 

 more specialized. The union of the spines into a thin 

 dorsal fin is far more probable and the idea is supported 

 by the presence of rugosities and the channels of small 

 nutrient vessels such as would lie beneath a thick dermal 

 covering. The anterior and posterior faces of the bases 

 of the spines have sharp, low ridges which give place to 

 shallow grooves farther up the spine ; only near the top 

 are the spines similar on all sides. Moreover in the liv- 

 ing genus Basiliscus, which has elevated dorsal spines, 



