12 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.37. 



vertebral column, including the terminal caudal centrum (45 centra 

 preserved) ; portions of 27 pairs of ribs; three distal carpalia of the 

 left hand; first digit of the left hand entire, and others represented 

 by scattered phalanges, four digits in all ; left foot nearly entire, lacks 

 only terminal phalanx for digit III ; right foot complete but elements 

 scattered, both legs otherwise complete ; portion of pelvis. 



The reptile, to which the remains j^ertain, must have been an 

 aquatic, or at least a semiaquatic form, if one may judge from the 

 expanded foot, although the limbs show no adaptive modifications for 

 aquatic conditions. The dimensions of the foot, as preserved, how- 

 ever, sho^^' a broad surface, which may be given the same interpre- 

 tation as McGregor has given the foot of Mesosaun/si Jjtrtsiliensis 

 McGregor," from the Permian of South America. 



The long tail in the present species would tend to sup]^ort the idea 

 of the aquatic habit of the animal, although there is not the slightest 

 evidence of lateral flattening, nor are elongate spines and chevrons 

 present as in Mesosatn-us hrasiliensis McGregor. The stout, elongate 

 femur in the present species is in strong contrast with the crocodile- 

 like femur of Mesosaurus. The femur resembles, in its proportions, 

 that of /Sai/rarus costei Thevenin, from the Carboniferous of France.'' 

 In view of the character of the beds from which hodectes comes and 

 the aquatic nature of the Microsauria which were associated with 

 Isodectes, it will not be far wa'ong to assume an aquatic habit of life 

 for Isodectes for at least a part of the time. The clawed phalanges 

 are to be looked on as indicating a partial adaptation to land 

 dwelling. 



The form of the body of Iwdectes puncti/latiis Cope is remarkably 

 lizard-like and resembles in its proportions some of the larger 

 species of Iguana without the great length of tail. The vertebral 

 column in Isodectes was solidly built and its limbs were strong, being 

 supported, in the pelvic region at least, by a strong arch. 



It is extremely unfortunate that the entire skeleton of the reptile 

 was not preserved, since there is no doubt that it was all embedded 

 in the coal if we may judge from the nature of the fracture extend- 

 ing across the anterior region of that portion of the skeleton which 

 is preserved, but in the violent processes of mining the anterior por- 

 tion of the body was lost. As a matter of coincidence the same acci- 

 dent may be mentioned as having occurred in the case of Saiiravus 

 costei Thevenin. The vertebral column in Isodectes consists of bi- 

 concave centra with possibly rudimentary intercentra, although no 

 definite evidence is to be had on this head. The spines of the verte- 

 brae were low and almost rudimentary. The notochord was probably 



« J. H. McGregor^ Relatorio Final Conimissao de Estudos das Minas de Carvao 

 do Brazil, 1908, p. 303. 



*A. Thevenin. Anuales de Paleontologie, vol. 1, 1903. pi. 2. 



