400 ■ HARRIS HAWTHORNE WILDER ON 



what greater size of the neural canal in comparison with the haemal, and a consequent 

 greater heiglit of the anterior portion of the neural arch, which in this region becomes 

 prolonged and tubular. 



A common phenomenon in these last caudal vertebrae, beyond about the oSth, is 

 an antero-posterior bifurcation or doubling of either the neural or the haemal spines or 

 both. Frequent examples of this are noticed in the accompanying figure (fig. 5), in 

 which appear several grades of this malformation, from a bifurcation of the free end to 

 what seems to be a complete doubling of the spiue. This phenomenon is referred to 

 by Bumpus ('97) and figured in some of his radiograph illustrations. 



Sternum. 



The several cartilaginous rudiments which represent this part in Necturus are some- 

 what difficult of detection and thus entirely escaped the attention of the earlier investi- 

 gators. They consist of a number of thin cartilages found in several successive myocom- 

 mata of the pectoral region and confined mainly to the area covered by the overlapping 



X 



^^' x^ "^x 



■-..../V-./- 



B C D t 



Fig. 6. Sternal pieces of six different individuals, sliowing variation. 



epicoracoids. As will be seen by text figure 6, which represents the sternal elements 

 of six normal individuals, the cartilaginous pieces show great individual diit'erence in shape 

 and size, and are capable of some vai'iation in the myocommata involved. The largest 

 sei'-mental portion or sternebrum is that of the 4th myocomma which is in general an 

 irregularly triangular or often bat-shaped piece. It lies just posterior to the epicoracoids, 

 in the angle formed b}- their overlapping edges, and is sufficiently large and .superficial to 

 give rise tb a part of the fibers of the pectoralis muscle. This muscular attachment as 

 well as its position relative to the shoulder girdle fixes its identity as the homologue of 



