150 



Mr. C. T. Retail on a remarkable 



length and tlie genital opening at its posterior end, just behind 

 the articulation of an external movable, for ward ly directed, 

 serrated bone ; anteriorly the appendage ends in a long 

 slender bone extending forwards to beneath the chin, curved 

 towards the side on which the serrated bone lies and away 

 from that on which the vent opens. 



Pliallostethus dunckeri, sp. n. 



The form and proportions are shown by the accompanying 

 figures. I count 8 to 10 dorsal and 26 to 28 anal rays ; the 

 caudal fin is imperfect in all, so that its exact shape is 

 uncertain ; there are about 40 scales in a longitudinal series, 

 and they appear to correspond to the myotomes, so that the 

 vertebra? number about 40. Of seven specimens (three males 

 and four females) the largest male measures 25 mm., the 

 largest female 29 mm. in total length. 



The external features of the lower surface of the head and 

 abdomen in the female fish are illustrated in fig. 2. A flattish 



Fiff. 2. . 



a pv o f r 



Phallostethus dunckeri, head and abdomen of female from below ( X 8). 



a., anus ; pv., pelvic fin ; o., opening of oviduct ; u,, urinary opening ; 

 /., dermal fringe ; gr., groove. 



median naked area margined anteriorly by the lower edges 

 of the hypocoracoids expands backwards and contains suces- 

 sively the vent, a pair of almost vestigial pelvic fins, the 

 genital and urinary apertures ; from the last a low median 

 keel runs backwards. Behind the opening of the oviduct 

 the naked area contracts, and it becomes a groove, which 

 extends to the origin of the anal fin, becoming narrower and 

 deeper posteriorly ; the walls of the groove are supported by 

 the ends of the seven pairs of ribs. 



