14 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. i. 



ker indicates, the neural arches of these vertebrae. These arches have 

 become expanded anterio-posteriorly and have coalesced. Belonging 

 lo each of these arches is a haemal arch in the form of a hypural 

 bone. Each is co-ossified with the under side of its proper vertebra 

 just as is the last hypural belonging to the last so-called complete 

 vertebra. The last three of the haemal arches are directed nearly 

 horizontally backward. These are followed by two other similar 

 bones, which Kolliker says belong to the last vertebra, the hinder- 

 most looking like a continuation of the vertebral column. On this 

 point I shall have something to say when I come to speak about the 

 microscopic structure of these parts. 



Lying between the bone last mentioned and the cartilage which 

 is prolonged behind the ossified centra, Kolliker describes another 

 similar bone which does not reach the last centrum. It functions as 

 .a ray-bearer, and doubtless is the lower arch of a vertebra which has 

 ceased to attain development. I find this bone in two specimens. 



Kolliker describes that portion of the cartilage which projects 

 beyond the last vertebral body as consisting of a tube which incloses 

 the spinal cord, or its representative. On the underside of the carti- 

 laginous rod is a furrow, at first shallow, and in this lies the noto- 

 chord. Posteriorly the furrow deepens, and at length, near the ter- 

 mination of the cartilage, the notochord is enveloped in the substance 

 of the cartilage. Everywhere there is, according to Kolliker, a 

 partition of cartilage between the notochord and the spinal cord. 

 This matter will come up for consideration later. Kolliker regards 

 the extension of cartilage behind the last vertebra as representing 

 not only the upper arches but also the continuation of the vertebra] 

 bodies. It thus represents a cartilaginous vertebral column ("eine 

 ganze knorpelige Wirbelsaule darstellt"). 



The tail of Amia has not attained the stage of complete hetero- 

 cercality, that is, it*s not hypocercal. There are still a few fin-rays 

 lying above the vertebral axis. Of these epural fin-rays, Kolliker 

 figures five, all unsegmented. Shufeldt figures apparently three, 

 all much segmented. The specimens which I have examined show 

 three rays, only the most posterior being segmented sparingly. Of 

 epural interspinous bones, Kolliker figures four, the most posterior 

 being one which lies closely against the upper side of the prolonged 

 cartilage. Shufeldt figures six interspinous bones', the hindermost of 

 which is apparently the one which lies close to the rod of cartilage. 

 This series of bones, as shown by the author last named, completely 

 fills up the space between the last dorsal ray and the upper border of 

 the caudal fin. He is of course in error when he states that these 



