BY J. DOUGLAS OGILBY. 413 



(2). " The upper lip is flat and considerably prolongated over 

 the buccal aperture." 



This inferior position of the disk is also true of Mordacia and 

 Veliisia, but not of Geotria. 



(3). "The lateral line is well marked in all the length of the 

 body." 



In my two adult examples of the Narrow-mouthed Lamprey 

 there is a conspicuous series of open pores down the middle of 

 each side of the body, homologous to the lateral line in the true 

 fishes; in neither of the other genera is there any trace of such 

 line. 



(4). " There is only one dorsal, which begins at about two- 

 thirds of the length of the body and is joined with the caudal 

 and anal." 



The posterior position of the origin of the dorsal fin is a distinct 

 character of the Australian Petromyzonids, and entirely precludes 

 the possibility of this example being a larval Mordacia, in which 

 genus the fin commences in the adult at no great distance — one- 

 fourth to two-fifths — behind the middle of the body, and it is not 

 conceivable that the permanent anterior portion of the fin should 

 develop after the metamorphosis has taken place, rather than 

 that it should be isolated by the absorption of the intervening 

 membrane. The want of accuracy in the expression " about two- 

 thirds " makes it impossible to judge absolutely between the 

 claims of Velasia and Geotria, but the balance is somewhat in 

 favour of the latter, in which the insertion of the dorsal fins in 

 the adult is distinctly more posterior than in the former. 



Tlie continuity of the two dorsal fins and of the second dorsal 

 with the caudal is merely indicative of the ammocoetal character 

 of the individual, as also is the absence of eyes and teeth. 



Two other characters in Castelnau's description apparently 

 favour the claims of Geotria; namely, that the body " is entirely 

 divided in aniaular rings " and that " the skin of the throat is 

 rather extensilile." 



