400 HARRIS HAWTHORNE WILDER ON 
what greater size of the neural canal in comparison with the haemal, and a consequent 
greater height 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 38th, 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 spine. 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 
A B C D E f: 
Fig. 6. Sternal pieces of six different individuals, showing 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 difference in shape 
and size, and are capable of some variation in the myocommata involved. The largest 
segmental portion or sternebruin 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 by their overlapping edges, and is sufficiently large and superficial to 
give rise to 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 
