THE LAMPREYS AND HAGFISHES 



2931 



the exception that there is no instance among the latter where a species is common 

 to Australia and South America. 



The hagfishes, of which there are two genera, constitute a family 



{Myxinidce} distinguished from the last by the nasal sac having a 

 posterior duct which perforates the palate; the single external nasal aperture being 

 situated above the mouth at the extremity of the head, which is furnished with 

 four pairs of barbels. The mouth is devoid of lips, the palate is provided with a 

 single median tooth, and there are two comb-like series of rasping teeth on the 

 tongue. The gill apertures, or aperture, are situated at a considerable distance 

 from the head; and each gill pouch has a separate duct opening into the oesophagus. 

 The sides of the abdomen carry a row of mucous sacs, and there is no spiral valve 

 to the intestine. The large eggs are invested in a horny envelope, furnished with 

 threads for adhesion. In the true hagfishes, of which the common species (Myxine 

 ghitinosa] is found on the coasts of Europe and North America, there is but a single 

 gill opening on each side of the abdomen, leading by means of six ducts to as 

 many gill pouches. Another species has been recorded from the extremity of 

 South America; and the range of the genus also includes Japan. In the second 

 genus (BdeUostoma) t of which there are two species from the coasts of the South 

 Pacific, there are six or more gill openings on each side, each communicating by a 

 separate duct with a gill chamber. All these creatures are marine, and are fre- 

 quently found deeply buried in the bodies of fishes, more 

 especially members of the cod family, into which they 

 bore for the purpose of feeding on the flesh. They are 

 totally blind, and secrete vast quantities of slime, which 

 seriously interferes with fishing in localities where these 

 creatures abound. Met with in the fjords of Norwa} r 

 at a depth of about seventy fathoms, hagfishes have 

 been dredged from depths of nearly three hundred and 

 fifty fathoms. 



The Old Red Sandstone of Caithness has 



yielded the skeletons of a small limbless 



creature (Pal&ospondylus) , which there is 

 little doubt must be regarded as one of the forerunners 

 of the modern lampreys. Measuring only about a 

 couple of inches in length, these skeletons show a well- 

 calcified skull, while the notochord is surrounded by a 

 series of calcified rings, and the tail has a large fin, of 

 which the supports on the upper side are forked like those 

 of lampreys. The front of the head has a circular opening 

 surrounded with a ring of tentacles (dc, Ic), probably 

 corresponding to the nose of a modern lamprey; the 

 opening of the nose itself (n} appears to be single and 

 there are a pair of plates (JT) behind the head not 

 improbably representing gill plates. It may be confidently assumed that this little 

 creature is but one among a series of lost types. 



Primeval 



Lampreys 



SLIGHTLY ENLARGED RESTO- 

 RATION OF THE SKELETON 

 OP THE PRIMEVAL LAM- 

 PREY. 



(After Traquair.) 



