614 MR. J. DOUGLAS-OGILBY ON [DeC. 6, 



or a child with the proportions of a full-sized adult. All these dis- 

 tinctions therefore, instead of indicating diversity, are rather conclusive 

 evidence of affinity, unless size itself is to be considered as a worthy 

 ground of generic distinction. 



After all a generic name is purely a matter of convenience, and for 

 my part I think it more desirable and instructive to call the Liberian 

 species Hippopotamus, and thereby to indicate its close relationship 

 with the well-known large animal of that name, than to give it a 

 designation in which this affinity is lost sight of. It may be some- 

 times expedient to divide up genera in which the number of species are 

 excessive upon comparatively trivial characters ; but in the case of 

 Hippopotamus, with only two living and but few extinct species, no 

 such reason can be alleged. 



4. On a new Genus and Species of Australian Mugilidse. By 

 J. Douglas-Ogilby, Department of Fishes, Austr. Mus. 

 Sydney. (Communicated by F. Day, C.I.E., F.Z.S.) 



[Eeceived November 1, 1887.] 



Trachystoma, gen. nov. 



Branchiostegals six ; pseudobranchise present. No adipose eye- 

 lids. Vomer and palate furnished with distinct bands of villiforra 

 teeth ; jaws toothless. Scales rather small, finely ctenoid. 



Trachystoma multidens, sp. nov. 



B. vi. D. 4i. A. 3/9. V. 1/5. P. 15. C. 14. 

 L. lat. 48-51. L. tr. IG. 



Length of head 55 to b\, of caudal fin 4| to 5^, height of body 

 4| to 5 in the total length. Eye without adipose lids, the diameter 

 of each 4| to 4g in the length of the head, li to I5 diameters from 

 the end of the snout, and 1^ diameters apart. luterorbital space 

 convex ; snout broad and depressed ; upper lip not thickened. 

 Angle made by the anterior edges of the mandibles moderately 

 obtuse ; the length of one of the mandibular rami is f, or slightly 

 more, of the width of the gape of the mouth. The maxilla reaches 

 backwards to the vertical from the hinder margin of the posterior 

 nostril. Preorbital serrated along its outer edge. Nostrils nearer 

 to the eye than to the end of the snout ; the anterior nearly circular, 

 small ; the posterior oval, large, about five times the size of the 

 anterior. The free space on the chin is cf moderate size and lan- 

 ceolate. Teeth : a patch of villiform teeth on the vomer, some- 

 times crescentic, sometimes biclavate ; palate with an elongate 

 band, broadest anteriorly. Fins : Spinous dorsal commences rather 

 nearer to the base of the caudal than to the tip of the snout ; its 

 spines are strong, the first the longest, about two thirds of the length 

 of the head ; the interspace between the two dorsal fins is rather 

 less than the base of the spinous dorsal, while the distance between 

 the origins of the two dorsals exactly equals the length of the head, 



