594 MR, G. A. BOULENGER ON THE [NoV. 17, 



To render my synopsis perfectly intelligible, it is, however, neces- 

 sary to say a few words, by way of introduction, concerning the 

 external structure of the Tadpole and the manner in which its cha- 

 racters are described. 



1. The Form. — The head and body are so fused that it is ex- 

 tremely difficult to discern the limit between the two. The term 

 body is therefore used as meaning both head and body. Its longitu- 

 dinal measurement is taken to the origin of the hind limbs. The tail 

 consists of a fleshy muscular portion bordered above and below by 

 membranous expansions, termed respectively the upper and loioer 

 crest. By depth of the tail is meant its greatest depth, crests 

 included, and the length is measured from the posterior extremity 

 of the body. 



2. The Mouth. — This term is used in its wider sense, i. e. to 

 include the much-developed Up, surrounding, like a funnel directed 

 downwards, the horny beak (fig. 1, m.), not unlike that of a 

 cuttlefish, which forms the entrance to the mouth proper (b.o.'). 

 The characters offered by this circular lip are among the most im- 

 portant for the distinction of species, and have formed the subject of 

 a valuable paper by Heron Royer and Van Bambeke (Arch, de Biol, 

 ix. 1889), to which I have already referred and shall often have to 

 refer again. This lip may be entirely bordered by fleshy papillce 

 (I. p.), or these may be restricted to the sides or to the sides and the 

 lower border. Its inner surface is furnished with ridges armed with 

 series of minute, bristle-like, erect horny teeth (fig. 1, t.), each of 

 which, when strongly magnified, is seen to be formed of a column of 

 superposed cones, hollowed out at the base and capping each other ; 

 the summit of each of these cones is expanded, spatulate, hooked 

 backwards, and usually multicuspid. By drawing an imaginary 

 line across between the mandibles, the lip may be divided into an 

 upper and a lower portion, the series of teeth above the upper man- 

 dible being termed upper labial, those below the lower mandible 

 being lower labial. These are described as 1st, 2nd, 3rd, &c., pro- 

 ceeding from the outer border towards the beak in both the upper 

 and the lower lip, as shown in the accompanying figures. Each 

 series is reckoned as one, whether continuous or more or less 

 interrupted in the middle. This method of describing appears to 

 me far more simple, and at the same time more correct, considering 

 the great amount of individual variation, than that used by the 

 authors named above, who distinguish between "median" and 

 "lateral" series according as to whether or not the series is broken 

 up in the middle. The first series, either in the upper or lower 

 division of the lip, may be marginal (fig. 1, A, ^.1), or it may be 

 within the border, which is then occupied by fleshy papillse (fig. 1, B). 

 I have expressed the arrangement of the series of teeth by formulae — - 

 3, for instance, indicating the number in the upper and lower 

 divisions of the lip, the figures being separated by a transverse line 

 corresponding to the position of the horny beak. The labial teeth 

 are usually arranged in a single row on each ridge (fig. 1, A) ; in the 



