239 



far apart. Mouth very large, surrounded with rather large, trans- 

 verse, torn leaves. 



This genus chiefly differs from Felasia in the rudimentary state 

 of the lower internal tooth, in the form of the labial teeth, in the 

 large size of the oral disk, and the extraordinary development of the 

 throat-pouch, which is found in a rudimentary state in the Petro- 

 myzon marinus. This development of the pouch is perhaps to adapt 

 the animal to the long drought of the Australian rivers. 



1 . Geotria AusTRALis. PoucHED Lamprey. (Pisces, PI. V.) 

 Hah. South Australia. Fresh water. 



4. VELASIA. (Pisces, PI. IV. fig. 4.) 



Upper internal teeth large, transverse, crescent-like, divided into 

 four flat, elongated lobes ; the outer lobes largest. The lower inter- 

 nal teeth large, transverse, crescent-like, convex, denticulated on the 

 edge. The labial teeth very numerous, truncated, in crowded, arched 

 series, diverging from the throat ; the inner ones large, and gra- 

 dually diminishing in size to the edge. Tongue with two very large, 

 long, curved teeth, with a triangular plate beneath at their base. 

 Dorsal fins two, far apart. Mouth moderate, edged with transverse 

 foliations. 



1. Velasia chilensis. Chilian Lampern. 

 Hah. Chili. In fresh water. 



5. CARAGOLA. (Pisces, PI. IV. fig. 5.) 



Upper inner teeth two, large, separate, lateral, submarginal, each 

 with three acute tubercles. Lower inner teeth large, crescent-shaped, 

 nine-lobed ; the central and two lateral lobes on each side larger. 

 The labial teeth in a subcircular, submarginal series, large, trans- 

 verse, band-like, with three or four tubercles. Tongue with two flat- 

 tened teeth, and a triangular, transverse plate below, with an acute 

 process between the teeth on the upper edge. Dorsal fins two, far 

 apart. 



1. Caragola lapicida. Caragol. 

 Hah. West Coast of America. 



6. MORDACIA. (Pisces, PI. IV. fig. 6.) 



Upper inner teeth two, separate, lateral, subtrigonal, each with 

 three tubercles. The lower nine conical, acute, in an arched series ; 

 the five central smaller. Labial teeth small, conical, in a single, cir- 

 cular, submarginal series, with a single, additional, odd tooth in the 

 centre above. Tongue with two conical, arched teeth. (Rich. Voy. 

 Erebus & Terror, t. 38.) 



Petromyzon, sp.. Rich. Voy. Erebus & Terror, t. 38, 1845. 



