418 MONOGRAPH OF TilK AUSTRALIAN MARSlPOBRAyCHlT, 



of the first dorsal is erroneously given as 6i inches; this is an 

 evident lapsus calami for 1^ inches. 



Taking all the characters which I have referred to above, for 

 or against, together I consider that I am quite justified in my 

 association of Castelnau's species with Velasia stenostomus. 



Petromyzon sp. 



Kner's description of the ammocrete from the Waikato River, 

 New Zealand ( Voy. Novara, Fisch. p. 421) gives no characters on 

 which any accui'ate judgment as to its relationship can be based; 

 the remark, however, that "the cavity of the suctorial disk is 

 closely beset with papillte " is clearly more indicative of aflinity to 

 Velasia than to Geotria. Giinther is, therefore, probably right in 

 conjecturing that "it is perhaps the young state of" Geotria 

 cliilensis ( = Velasia stenostomus). 



There is, however, one other character given by Kner which 

 puzzles me ; he says : — " The large triangular nostril lies nearly 

 above the margin of the sucking disk in the middle of the fore- 

 head." Now in none of the species is the nostril situated " in the 

 middle of the forehead," though it is of course placed on the 

 middle longitudinal line of the head between or nearly between 

 the anterior borders of the eyes; again the posterior margin of 

 the suctorial disk does end beneath the middle of the forehead, 

 i.e., of the preorbital space, in Velasia, but not beneath the 

 nostril; it ends beneath the nostril only in Mordacia, which genus 

 is not found in New Zealand; if it were I should unhesitatingly 

 consider this little animal to be the larval form of the latter 

 genus. 



Breeding: — As with Sfordacia mordax nothing definite is 

 known of the propagation of this species, but it is worthy of note 

 that such ammoccetes as have hitherto been recorded were all 

 obtained in tidal waters, and as before their metamorphosis these 

 animals remain buried in the mud, it would appear that the adults 

 do not necessarily seek fresh water before depositing their spawn, 

 nor is the purity of the element requisite to the development of 

 the ovum. 



