PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



35 



in Diasparactus the second plays little part, as indicated above. For the reasons 

 cited in the description of the foot, we are of the opinion that the Diadectidae were 

 not aquatic animals, but marsh-dwellers; we believe these animals to have been 

 very sluggish, harmless eaters of vegetation or small invertebrates, and to have 

 been able to present no more than a passive defense against the attacks of the 

 larger carnivorous forms, pelycosaurs, or forms yet unknown. Such habits would 

 inevitably lead to concealment and to the persistence of any forms favored by the 

 development of some form of protection, as an armor. We know that the period 

 in which these animals lived was one of those, frequently repeated in the history 

 of the world, in which there was a keen contest between attack and defense, the 

 development of a peculiarly efficient type of predatory form (in this case the 

 pelycosaurs of the genus Dimetrodon) was paralleled by the development of armor 

 on the weaker forms (in this case both amphibians and reptiles) . It is very probable 

 that Diadectes followed the general trend. The lateral position of the orbits does 

 not indicate habits such as those of the Stegocephalia, in which the orbits are near 

 the surface of the skull and look largely upward. It is possible, but only offered 

 as a suggestion, that the large size of the orbit may indicate a large eye and so 

 nocturnal or crepuscular habits. 



Measurements. 



Total length of the animal, as restored 1.35 



Length of 10 vertebrae added to complete the 



tail 105 



Length of skull, as restored 167 



Width of skull, across quadrates, as restored . . .154 

 Length of arc of slightly flattened right clavicle .159 



Length of arc of right scapula 180 



Width of anterior end of same 128 



Extreme length right humerus 151 



Width proximal end of same 084 



Width distal end of same, slightly distorted . . . .094 



Width distal end left hiunerus 081 



Length right ulna 1 18 



Length right radius 084 



Length complete third digit of manus, left side .073 



Length metacarpal of same digit 026 



Width proximal end of same 024 



Height of ninth vertebra 117 



Breadth across posterior zygapophyses of same .074 

 J^ength across anterior-posterior zygapophyses. 



same 039 



Length bottom line of centrum, same 0.023 



Height of fifteenth vertebra 134 



Breadth across posterior zygapophyses of same .084 

 Length across anterior-posterior zygapophyses 



of same 038 



Length of bottom line of centrum of same 029 



Length of bottom line of pelvis 166 



Height of pelvis to top of ilium, a little ex- 

 aggerated by pressure 016 



Length of crest of right ilium 1 16 



Breadth across center of acetabulum 092 



Length of right femur 146 



Length of right tibia 102 



Length of right fibula 118 



Approximate breadth of tarsus 082 



Length of fourth digit of pes, right side, minus 



terminal phalange 086 



Length of metatarsal of same 037 



Length of first digit of pes, left side 045 



Breadth of proximal end of metatarsal of same .023 



