.Mr. R. Walker on the Anatomy o/ Regalecus. ~To 



each side, to join the skin; other two proceeded downwards, 

 and formed the lining of the abdominal cavity, at the lower edge 

 of which they again coalesced, enlarged, and extended down to 

 the ventral margin. The septa or bands connecting the lining 

 membrane of the abdominal canty and the coriurn were very 

 numerous, from a little below its commencement down to the 

 ventral edge of the fish. 



The vertebral column appeared to be only a stage in advance 

 of the primitive notochord, and presented no appearance exter- 

 nally of being segmented, but looked like a continuous flexible 

 column, without any prominence or depression to indicate where 

 the segments were. The only inequality visible was a slight 

 depression on the sides between the neural and haemal arches. 

 The column had a somewhat hexagonal appearance externally, 

 which was partly caused by its enveloping-membrane thickening 

 along the middle of each side, where it proceeded outwards. 

 When the column was bent from side to side, the joints were 

 apparent ; and when cut open, there was a slight depression ob- 

 served at the joints, which was caused by the cartilage of each 

 segment or vertebra not quite meeting that of the next. 



The centra of the vertebras were composed of what to the un- 

 aided eye appeared to be simple cartilage, and were entirely de- 

 void of ossification ; they measured on an average about If inch 

 in length, and had the appearance of gradually shortening, 

 the centra of the posterior end being slightly shorter than those 

 of the anterior. Each centrum was hollowed out internally at 

 both ends into a conical or hourglass-shaped cavity. The apices 

 of the cavities were separated from each other in the middle of 

 the centra by a layer of cartilage about j 1 ^ inch in thickness, 

 through which there was a small perforation, virtually connect- 

 ing them together. The vertebral centra were ^ inch in dia- 

 meter, their contiguous cup-margins being very thin, scarcely 

 amounting to yV inch. The cavities of the centra of the verte- 

 bral column were round internally, and were filled with a gela- 

 tinous-looking substance of sufficient consistency to retain its 

 conical shape at both ends after being removed. This substance 

 had been the base of the primitive embryonic chorda dorsalis, 

 around which the cartilage had afterwards been developed. 

 In its latter condition it consisted of alternate swellings and 

 contractions corresponding to the internal shape of the column ; 

 in this form it had extended, in all probability, the whole length 

 of the body. The neurapophyses consisted of narrow pieces of 

 cartilaginous-looking lamina? developed in the walls of the mem- 

 brane which formed the neural canal. At their lower ends they 

 were firmly anchylosed to the middle of the centrum of each of 

 the vertebrae ; at their upper ends they coalesced at the same 



