16 Mr. R. Walker on the Anatomy of Regalecus. 



point as the membrane, and in this way they formed a series of 

 rudimentary neural arches. The neural spines were about 

 3^ inches long, and consisted, as well as the arches, of what 

 appeared to be the hardest cartilage in the fish ; they were con- 

 fluent and perhaps connate with the neurapophyses, from which 

 they extended up to a little beyond the commencement of the 

 interneural spines. These neural spines were slender, flexible, 

 and not easily recognized in the central membranous partition 

 already referred to, in the walls of which they were developed, 

 and remained imbedded. The interneural spines commenced 

 about 4^ inches below the dorsal margin. They were at first 

 small, thread-like, and quite hid in the enveloping membrane, 

 but gradually enlarged as they approached the dorsal margin, 

 where they were about |- inch across. These spines began to 

 expand on both sides, before and behind, about half an inch from 

 their upper extremities. This expansion went on increasing till 

 each spine was half an inch in breadth, when the enlarged or 

 projecting portion joined that of the spine next to it, before 

 and behind, and thus formed a continuous cartilaginous and 

 strengthening ridge extending along the dorsal margin. The 

 lateral projections of the interneural spines did not extend quite 

 to the upper edge, but sloped away a little from the middle of 

 the upper ends of the spines downwards on both sides, which 

 formed a series of notches extending along the upper edge; each 

 notch corresponded to, and was placed immediately above, the 

 junction of each pair of spines. In these notches or cavities 

 oval-shaped pieces of cartilage were placed, and held by liga- 

 ments, which allowed them a free motion principally from side 

 to side ; to these cartilages the bifurcated fin-rays were attached. 

 There was a small disk-like addition on each side of the lower 

 ends of these double rays, which was in contact with, and firmly 

 held by ligaments to, the lateral surfaces of the oviform carti- 

 lages. The dorsal fin-rays were bifurcated for a considerable 

 part of their length ; it is very likely that they were confluent at 

 the points, but of this I am not certain, as none of them were 

 entire. For upwards of two inches of their length, however, 

 they appeared to have had only a membranous connexion. 



The parapophyses existed as cartilaginous laminse developed in 

 the membranous walls of the hsemal canal, anchylosed at their 

 upper ends to the middle of the lower sides of the vertebral 

 centra, and coalescing at the lower ends about three-eighths of 

 an inch below the vertebral column ; in this way they formed a 

 series of contracted haemal arches, which contained the aorta 

 and the vena cava. There were thread-like hsemal spines con- 

 fluent with and proceeding downwards from the parapophyses, till 

 they were finally lost in the walls of the membrane a little above 



