PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



33 



Fig. 20. — Diasparactus zenos Case. Lateral 

 view of the ninth to the twenty- third cau- 

 dal vertebrae, X K- 



From this point back the character of the vertebrae changes regularly and very 

 slightly. The last trace of a rib is seen on the eleventh or twelfth. The sixteenth 

 and seventeenth still have well-formed neural arches located on the anterior half 

 of the centrum; the posterior zygapophyses are elongated. From this point back 

 to the twenty-third, the' last preserved, the neural spines are low, almost rudi- 

 mentary, and the zygapophyses are elongated, interlocking strongly at first, but 

 becoming reduced in the posterior part of the tail. In only the last few vertebra 

 is there any tendency for the centra of the vertebrae to become at all elongate, 

 and even here it is very slight. There is no indication of any great length of tail. 

 The ribs: Anterior to the first vertebra in series, reckoned as the third cervi- 

 cal, there is a well-developed rib, of moderate 

 length, lying in the matrix just within the edge 

 of the scapula. This is the rib of the axis ; it 

 has a wide, undivided head and a slender shaft 

 terminating in a point. The ribs of the third, 

 fourth, and fifth vertebrae are in general form 

 similar to the ribs of the same vertebrae in 

 D. phaseolinus, but as they are injured on the 

 left side and covered by the scapula on the 

 right, the exact form can not be given. The 

 rib of the third vertebra (fig. 21 a) has an 

 elongate, undivided proximal end; beyond this it contracts to a narrow shaft; the 

 anterior edge is straight to the distal end, but the posterior is extended backward 



in a sharp point almost at right angles to shaft for a centi- 

 meter or more and then obliquely forward to the distal end ; 

 this gives a narrow, triangular form to the rib, resembling 

 the same rib in D. phaseolinus, but longer. The shape of 

 the next two ribs is less certain, but they are larger than 

 the third and were evidently of the same triangular form. 

 The fifth is the largest of the series. The sixth rib is nor- 

 mal in form, with an undivided head. There is no trace of 

 the plates which overlie the sixth, seventh, and eighth ribs 

 in Diadectes. Beyond the sixth the ribs are not preserved 

 in place until the fifteenth and sixteenth are reached. On 

 the left side of the series from the eighth to the fifteenth 

 are attached the imperfect shafts of five ribs, but neither 

 the proximal nor the distal ends are preserved. The shafts, as preserved, are rather 

 more slender than in D. phaseolinus. On the left side of the fifteenth (fig. 2 1 b) and 

 sixteenth the ribs are retained in place, but are bent back parallel to the column. 

 The heads are rather short and are undivided; the shaft of the rib stood almost 

 directly out from the vertebrae, with little downward curvature. 

 There is no trace of any abdominal ribs. 



THE RESTORATION OF DIASPARACTUS ZENOS. 

 In the restoration presented (fig. 22) we believe that there is very little 

 that can be questioned. The skull, though badly shattered, presented nearly all 

 the characters, and its resemblance to both Diadectes and Animasaurus is so close 

 that we feel justified in all the points which we have recorded. Neural spines are 

 present both in sufficient number and in sufficiently diverse positions to render 

 certain their general characters throughout the column. The atlas is restored 

 in toto from Diadectes, but the presence of the atlantal and axial intercentra gives 



Fig. 21. — -Diasparactus zenos 

 Case.XJ^. A, rib of third 

 cervical vertebra from 

 left side; B, head of rib 

 attached to right side of 

 fifteenth vertebra. 



