396 MONOGRAPH OF THE AUSTRALIAN MARSIPOBliANCHII, 



Up to the year 1894 ichthyologists were content to segregate 

 the A^arious species of Lampreys in a single family, to which the 

 name Petromyzontidce had been given by Risso as early as 1826 

 {Eur. Mer'ul. Hi. p. 99), the title being altered six years later by 

 Bonaparte (Saggio, (&g. p. J/.!) to the more correct orthographic 

 reading Petromyzonidce. So long ago, however, as 1882 Dr. Gill 

 {Proc. U.S. Nat. Mus. v. p. 52 Jf) proposed to separate the genus 

 Mordacia ( = Caragola) from the remaining Hyperoart'd in a sub- 

 family Caragolinm. In the volume of the same pex'iodical for 

 1894 {p. 109) the same author went a step further and raised his 

 Caragolince to family rank under the name Mordaciidce, he having 

 in the meanwhile become reconciled to the use of Mordacia. 



In this later paper the author, in support of the proposed 

 family, pertinently remarks : — " It behooves those who may object 

 to these families to- consider why the character used to distinguish 

 them should not be of equal value with the union or separation 

 of the lower pharyngeal bones and like modifications generally 

 used." 



As Dr. Gill's contention appears to me to be perfectly sound, I 

 have accepted the families as here defined by him. 



Analysis of the Families of the Hyperoartii. 



Two distant lateral tuberculigerous laminie developed from the 

 upper arch of the annular cartilage .. 



MORDACIID^. 



A single median tuberculigerous suproral lamina developed from 

 the upper arch of the annular cartilage 



Petromyzonid^. 



There is one other character separating these two families, namely, 

 the labial fringes, which taken in conjunction with the more perfect 

 dentition of the former, appears to me worthy of special notice; 

 all the Petromyzonidce are provided with a more or less con- 

 spicuous fringe of papillae around the outer rim of the suctorial 

 disk, which fringe is rudimentary in Mordacia. If we look upon 

 these papillfe as having developed from the oral barbels of the more 

 ancient Hyperotreti — and in so doing I scarcely think that we are 



