MYXINIDAE. 



117 



muscles ; intestine without spiral valve ; gall bladder present ; egg large 

 with horny case provided with threads for adhesion ; marine in temperate 

 regions of both hemispheres. Myxine L., hag-fish, with six pairs of bran- 

 chial sacs opening by one external opening on each side. Bdellostoma 

 J. Miill. {Homea Fleming), with six or more (up to fourteen) branchia, 



Fig. 63. — Palaeospondylus gunni ventral view of head and side 

 view of vertebral column. tp trabeculo-palatine part of 

 skull ; pa parachordal part of skull ; d c, Ic, vc oral cirri ; a, 6, c, 

 n markings of more uncertain significance ; x post occipital 

 plates (from S. Woodward). 



apertures on each side, each leading to a branchial sac ; the number of 

 branchial sac3 may be different on the two sides of the body ; southern 

 hemisphere. Palaeospondylus Traquair, from the old Red Sandstone of 

 Scotland, is supposed to be a fossil Marsipobranch with calcified cartila- 

 ginous endoskeleton (Fig. 63). The notochordal sheath appears to have 



contained rings. 



