BY J. DOUGLAS OGILCY. 397 



assuming too much — it follows that both in this chai-acter as well 

 as in the dentition the Mordaciids have attained to a higher 

 degree of development than the Petromyzonids. 



Mordaciids. 



Caragolince, Gill, Proc. U.S. Nat. Mus. v. 1882, p. 524. 



Mordaciidce, Gill, Mem. Nat. Acad. Sc. vi. p. 129, 1893 {no 

 definition) and Proc. U.S. Nat. Mus. xvii. 1894, p. 109. 



Two distant lateral tuberculigerous laminae developed from the 

 upper arch of the annular cartilage. Labial fringe rudimentary. 

 Other characters similar to those of the Order. 



One genus on\j. 



Distribution : — Seas of South-eastern Australia, Tasmania, 

 and Chile; entering fresh waters for the purpose of breeding. 



MORDACIA. 



Caragola, Gray, Proc. Zool. Soc. London, 1851, p. 239. 



Mordacia, Gray, I.e. 



Body elongate and slender, subcylindrical in front, the tail and 

 a part of the body compressed; head small, oblong, attenuated, and 

 somewhat depressed, with slightly pointed snout; suctorial disk 

 moderate, oval, subinferior, extending backwards to the orbital 

 region, with a well developed simple external lip, between which 

 and the rim of the disk is inserted a regular series of short papillae; 

 rim of disk thin, forming a free, simple, cutaneous flap behind; sur- 

 face of disk feebly plicated on its outer, smooth on its inner moiety. 

 No gular pouch. * Branchial orifices small and subcircular, with a 

 low raised rim and a well developed valve inserted anteriorly. 

 Maxillary dentition consisting of two sul:)triangular plates, each of 

 which is provided with three strong, sharp, hooked cusps, arranged 

 in the form of a triangle; mandibular plate low and crescentic, 



* The Chihan Mordacia is said by Philippi to be occasionally provided 

 ^\ iih a gular sac ; this has never been observed in the Australian species, 

 and is most unlikely. 



