BY J. DOUGLAS 0G1LB\. 415 



The uninterrupted connection of the dorsal fin is of course only 

 significant as showing the immaturity of the individual, and is, 

 therefore, of no value as a generic character; this last sentence, 

 however, is sufficient to separate the species from Mordacia, in 

 which at all ages the dorsal and caudal tins are more or less 

 distinctly united, and in examples up to 125 millimeters are con- 

 spicuously so. 



The presence of " fringes round the mouth " is also peculiar to 

 Velasia and Geotria^ the external lip and discal rim of Mordacia 

 being almost smooth. 



The tenuity of the body and the absence of dilatation in the 

 head are, however, characters which belong to Velasia as opposfKi 

 to Geotria, and I have, therefore, decided to associate Castelnau's 

 N'rA) mordania howittii with Velasia stenostomus. 



Returning to the adult Lamprey, my reasons for considering 

 that Castelnau's specimen Avas Velasia stenostomus and not 

 Geotria artstralis as determined by him, will be found below, the 

 more important points of that author's description being taken 

 seriatim. 



(1). " The maxillai'y lamina is formed of four teeth, the 

 exterior of which are flat lobes, and the two interior ones long, 

 conical, pointed teeth." 



This gi-\'es a fair description of the maxillary cusps of Velasia 

 in which the inner cusps are as described and the outer are simple 

 and smooth, while in Geotria the inner cusps are lanceolate and 

 the outer notched and grooved. 



(2). " Suctorial teeth in numerous transverse series, those 

 situated backwards larger than the others." 



The number of the series of discal teeth in Velasia and Geotria 

 is about the same, but from the great expansion of the disk in 

 the latter they appear to be much less numerous than in the 

 former, to which, therefore, the wording of Castelnau's j)aragraph 

 would more naturally point; in Velasia too the posterior discal 

 teeth are as large as the inner lateral ones, while in Geotria they 

 are minute. 



