1 184 ON SOME ADDITIONAL LABYRINTHODONT FOSSILS, N. S. WALES, 



Ribs are attached to all the vertebrae, including those two 

 which the specimen retains behind the pelvis, or its indication. 

 I can best describe them by quoting direct from the Report often 

 cited above (Brit. Ass. 1873, p. 240.) " As to form they are 

 usually compressed (transversely to the axis of the trunk) at 

 either end, but are nearly cylindrical in the centre of the shaft. 

 They are short, relatively to the probable dimensions of the 

 thorax and strongly curved. A capitulum and tuberculum are 

 present in all well preserved examples. Both articular surfaces 

 are slightly concave and adjacent, and appear to have articulated 

 with the vertebral transverse process ; a notch or groove 

 commonly separates them, and is usually continued for some 

 distance along the shaft of the rib." Except for the ' strong curva- 

 ture' of the ribs, (1) the above description will be seen to correspond 

 with singular closeness to the specimen before us, if we take into 

 consideration the extremely immature and almost embryonic 

 condition of its ossification in general, together with the following 

 remarks upon Archegosaurus (I.e.) " Some very young examples 

 afford evidence of cartilaginous vertebral extremities, this evidence 

 consisting of the separation of the proximal ends of the ribs from 

 the vertebral column by a regular interval, and the hollowing out 

 of the ends as if in conjunction with cartilage ; at this stage a 

 transverse process may be seen to project for a short distance from 

 the lamina of the corresponding superior arch." Though this 

 account could hardly have been established upon our specimen, yet 

 it is plain that the specimen follows the diagnosis with curious 

 fidelity. The true head and tubercle of each rib, and the approaching 

 portion of the transverse process were evidently cartilaginous and 

 have quite disappeared. 



[In Gondwanosaurus the ribs display the general Labyrinthoclont 

 character — expansion at the two extremities, and articulation with 

 the transverse processes of the vertebrae by a distinct capitulum 

 and tuberculum.] 



(1) Owen, Paleontology p. 172, describes the ribs of Archer/osawu* as 

 " short, almost straight, expanded and flattened at the ends, round and 

 slender in the middle." 



