i2 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. i. 



show themselves as two linear pits running parallel with each other 

 and with the axis of the vertebra. In the more anterior vertebrae 

 they are nearly circular. Here they lie nearer the front end of the 

 vertebral body (Fig. 4). In the succeeding vertebrae the anterior 

 ends of the cartilages come close to the anterior ends of their respec- 

 tive centra, but become gradually more extended backward. Finally, 

 in the hinder two-thirds of the trunk they are so lengthened as to 

 occupy the whole of the length of the centra (Figs. 2 and 3). 

 These cartilages are found even on the vertebral bodies which are so 

 closely united with the head. They appear to have been noticed 

 only by Dr. M. Sagemehl (54, 57) who observed them on the verte- 

 brae at the hinder end of the skull and followed them backward along 

 the vertebral column. He states that in young individuals these car- 

 tilages penetrate deeply into the substance of the centra, while in 

 older specimens only thin plates of cartilage can be recognized rest- 

 ing superficially on the vertebrae. He enters into no explanation of 

 these structures. They will engage our attention later. We may, 

 however, note here, that in the case of three or four species of Amia 

 described by Dr. Joseph Leidy (44, p. 185, pi. xxxii.) from the 

 Bridger Beds of the Eocene of Utah, there occur on the lower side 

 of the vertebral body a pair of fossae, which occupy exactly the posi- 

 tion of the cartilages in Amia. The same fossae have been observed 

 and figured by Prof. E. D. Cope in species of Pappichthys, also occur- 

 ring in the Bridger Beds (17. p. 56, PI. iii.). They are spoken of 

 as two parallel fissures which further backward become oblong 

 fossae, and again near the caudal vertebrae are narrowed. Prof. Cope 

 further says that in the caudal vertebrae these fossae are as well devel- 

 oped as are the neurapophysial pits, and are much like them. He 

 evidently had in mind here the articulatory surfaces of the haemal 

 arches, which are very different things. 



The structure of the terminal portion of the vertebral column 

 has been more or less accurately described by Franque (26), Kolliker 

 (43), Wilder (59), and Shufeldt (57). Of these accounts it seems to 

 me that that of Kolliker is the most complete and his figures the 

 most accurate. Shufeldt presents an original figure of this region, but 

 he omits a representation of the cartilaginous elements, and, as it 

 appears to me, of some of the bones. Dr. Wilder had not seen Kol- 

 liker' s paper when he wrote his notes, and, through what appears to 

 have been a misunderstanding of Aug. Dumeril's language (25, ii. 

 401) he ascribed to Kolliker views not held by the latter author. So 

 far as they bear on the same points, Wilder' s results coincide with 

 those of Kolliker. 



