382 DESCRIPTIVE CATALOGUE OF AUSTRALIAN 1TSIIES, 



Sub-Class in. CYCLOSTOMATA. 



Skeleton cartilaginous and notochordal, without ribs and without 

 real jaws. Skull not separate from the vertebral column. Nbjimbs. 



Gill* in the form of fixed sacs without branchial arches, six or seven 

 in number on each side. One nasal aperture only. Heart w it/tout 

 bulbus arteriosus. Mouth anterior, surrounded by a circular or sub- 

 circular lip, suctorial. Alimentary canal straight, simple, without 

 ccecal appendages, pancreas, or spleen. Generative outlet peritoneal. 

 Vertical fins raged. 



Family PETKOMYZOXTIDJE. 



Body eel shaped, naked. Subject to a metamorphosis. In 

 tlio perfect stage with a suctorial mouth armed with teeth simple 

 or multicuspid, horny, sitting on a soft papilla. Maxillary, 

 mandibulary, lingual, and suctorial teeth may be distinguished. 

 Eyes present (in mature animals). External nasal aperture in 

 the middle of the upper side of the head. The nasal duct 

 terminates without perforating the palate. Seven branchial sacs 

 and apertures on each side behind the head. The inner branchial 

 ducts terminate in a separate common tube. Intestine with a 

 spiral valve. Eggs small. The larvse without teeth and with a 

 single continuous vertical fin. "Lampreys." 



Genus Mokdacia, Gray. 



Dorsal fins two, the posterior continuous with the caudal. 

 The maxillary dentition consists of two triangular groups, each 

 with three conical acute cusps; two pairs of serrated lingual 

 teeth. 



Chili and Australia. 



1127. Mobdacia moedax, Eichards. 



Yoy. Erebus and Terror, pi. 28. — Gunth., Cat. Fishes VIII. , 



p. 507. 



