184 Scientific Proceedings, Royal Dublin Society. 



The Vertebral Column. — The vertebral column consists of fifty- 

 four vertebrse, twenty of which are. abdominal, and thirty-four 

 caudal. Of the abdominal vertebrse, all but the two anterior are 

 provided with ribs, and all but the three anterior with parapo- 

 physes. The caudal vertebrae have well-marked haemal spines. 

 The body of the last vertebra is fused with a triangular plate of 

 bone, the coalesced hypurals. 



General Characters of Abdominal Vertebrce. — If a vertebra from 

 about the middle of the series (say the ninth, PL YIII., fig. 17) be 

 examined, it will be found to consist of a centrum, which is nearly 

 circular, slightly flattened from above downwards, a long neural 

 spine surmounting the .neurapophyses, and a pair of long parapo- 

 physes, which support a rib and an epipleural spine. The centrum 

 is amphieselous, the concavities being marked with concentric striae 

 of a whiter colour than the rest of the bone. On the under surface 

 is a longitudinal groove for the aorta, bounded on each side by a 

 prominent ridge, and lying somewhat to the right side, in the 

 floor of the groove, are two or three foramina. Outside the ridge 

 is a large depression, and next in order, from the lower part of the 

 side, springs the parapophysis, the base of attachment being 

 strongest in front. Above this a prominent ridge forms a sort of 

 second root to the para23ophysis, and the upper part of the side of 

 the bone is honeycombed with large and small foramina. From 

 the upper border of the bone in front springs the neurapophysis, 

 and behind the posterior zygapophysis. Between the two is the 

 "intervertebral" notch for the spinal nerves. The upper part of 

 the body is nearly flat, dotted over with small foramina. The 

 neurapophyses have the form of an elongated triangle. Springing 

 from the body by a comparatively narrow pedicle, they stretch 

 forwards over the posterior zygopophyses of the vertebra in front, 

 articulating with them, and thus forming the anterior zygopo- 

 physes. In front of this they nearly touch the neurapophyses of 

 the next vertebra, roofing over the intervertebral foramina. They 

 run directly into the neural spine, to which they are firmly anky- 

 losed, thus bounding the neural canal above. The neural spine is 

 dagger-shaped, being flattened from before backwards ; it inclines 

 backwards, continuing the axis of the neurapophyses. The pos- 

 terior zygapophyses are a pair of chisel-shaped spurs of bone, which 

 receiyo tho anterior zygopophyses between them ', the articular 



