NECTURITS MACULATUS. 



401 



the I'homboidal sternal plate of the higher Urodela, and it would seem probable that this 

 latter has resulted from the development of this piece alone. The sternebriun associated 

 with the 3d myocomma forms a long and slender open Y, which may or may not be 

 continuous with the steruebrum of the 4th. Sternal elements are often found both in the 

 2d and in the 5th myocomma, usually as a pair of cartilages, or as a unilateral piece. 

 Of these, the one associated with the 5th myocomma is much the more frequent, being 

 found in rather more than half of the specimens thus far examined, either upon one side 

 or both. Sternal elements in the 2d myocomma are rarely seen. 



Ribs. 



These have already been partly described with the transverse processes of the ver- 

 tebrae. In the larva they are cartilaginous and are directly continuous ^nth the two 

 cartilaginous rods enclosed in the osseous transverse process, and are thus bifurcated at 

 their proximal end. During the later process of ossification the 

 ribs become ossified as separate pieces and the cartilage remain- 

 ing between the proximal ends of the ribs and the sheaths of the 

 vertebral rods becomes di^dded across, thus furnishing two sets of 

 articular cartilages. By the shape of the first two ribs in the 

 adult, it would seem that both of the rods are equally involved and 

 simply fuse to form the ribs, but farther down the ventral or capit- 

 ular attachment retains its full size and importance, while the 

 dorsal one, although more in the same line with the free end, 

 becomes much reduced, and in many ^vertebrae its attachment is 

 merely ligamentous. Thus, described anatomically, the ribs of the 

 2d and the 3d vertebrae possess almost equal capitular and tuber- 

 cular heads, and show a tendency to become bifurcated at their 

 tips. In the ribs of vertebra 4 to 6 the two heads are still almost 

 equal but the distal part of tlie rib is a simple rod ; and fartlier 

 down, from about the 8th vertebra on, the capitular head forms 

 the main attachment, and meets at a decided angle the straight 

 piece formed by the free end and the tubercidar head. The sacral 

 rib possesses two very large and equal heads, but is not bifurcated 

 distally, and beyond the sacrum the rib element is a variable 

 quantity [v. suj).) . It would thus seem, judging from purely 

 anatomical evidence, that the condition described by Goppert 

 as characteristic of Necturus is not a universal one applicable to 



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/V2 



Fiir. 7. Hibs taken from 

 the right .^ide of the body 

 and pUiced .so a-s to .show 

 the anterior aspect. The 

 tubercular head i.s above 

 and tlie capitular below. 

 Tlie nunibere refer to the 

 vertebra to which each rib 

 belongs. X 2. 



