. Text-book of zoology for junior students. Zoology. OEDEES OF FISHES. 239 Order II. Marsipobranchii. This order includes the Hag-fislies [Mi/xinida-) and tlie Lampreys {Petromyzonido!), and it is defined by the following cliaiacters : The body is cylindrical and worm-like, and is destitute nf liniljs. The skull is cartilaginous, there is no lower jaw, and the notocliord re- mains through life. The mouth is circular and cup-like. The heart is composed of an auricle and a ventricle, but there is no hidbus arteriosus. The gills are pouch-like, communicating with the tlmjat on the one hand, and o
. Text-book of zoology for junior students. Zoology. OEDEES OF FISHES. 239 Order II. Marsipobranchii. This order includes the Hag-fislies [Mi/xinida-) and tlie Lampreys {Petromyzonido!), and it is defined by the following cliaiacters : The body is cylindrical and worm-like, and is destitute nf liniljs. The skull is cartilaginous, there is no lower jaw, and the notocliord re- mains through life. The mouth is circular and cup-like. The heart is composed of an auricle and a ventricle, but there is no hidbus arteriosus. The gills are pouch-like, communicating with the tlmjat on the one hand, and opening externally on the other by means of apertures placed on the sides of the neck, or on the ventral surface. The Hag-fish {Myxine) is an eel-like fish (fig. 172, A), which agrees with the Lampreys in having neither pectoral nor ventral. Fi;^. 172.—Morphology of Mar-sipobrancliii. A, Mii-iini; tjh'diio^n, llir ling lisli, s]iow- ing the sucker-like inoutli, and the two \'enti';il openings (/O liy wliicli Hie Wiitcr escapes from the gills. B, The Ri\'er Lamprey <:ir Laniperji {r<?trom;f:oii JIuriafilh), sliowing the seven branchial apertures on the side of the neck. fins, the representatives of the fore and hind himlis. The mouth is of a very remarkable character, and enables the Hag-fish to lead a very peculiar It is generally found embedded in the interior of some large fish, into whicji it has penetrated by means of a single serrated and recurved fang attached to the centre of the palate. The mouth itself is destitute of jaws, and foiuis a sucking disc or cup. Another remarkable peculiarity of ihe Hag-fishes is found in the structure of the nose. In all fishes, namely, except these and the Mud-fishes {Lepidosiren and i'cratodvs), the nasal chambers are closed behind, and do not communicate with the cavity of the mouth, as they do in the higher Vertebrates. In the. Please note that these images are extracted from scanned page images that may have been d
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