386 Dr. A. Giinther on Sexual Differences in Frogs and Fishes. 



the latter ichthyologist, that this difference extends also to the 

 pubic bones. In the male (PI. XVI. fig. A. A'.), the pubic bones 

 are convergent towards each other, and generally not perfectly 

 symmetrical in shape. The anterior portion of each of them is 

 composed of two broad horizontal plates, one above the other, 

 united for the greater part of their length, but separated by a 

 narrow fissure anteriorly. The upper plate is concave, spoon- 

 like, broadest anteriorly, and terminates posteriorly in a thick 

 oval knob, to which are joined the first two rays : the first thin, 

 small, rudimentary, without phalangeal joints; the second ex- 

 tremely thick and cuneiform. There is a stout metatarsal part 

 at its base, situated along the inner side of the first rudimentary 

 ray ; its length is nearly one-third of the entire ray. The lower 

 plate is twice as broad as the upper. The posterior portion of 

 the pubic bone is irregularly three-sided, broadest behind ; its 

 upper angle especially is thick and rounded. The broadest side 

 of this poi'tion has an oblique direction to the longitudinal axis 

 of the pelvis. 



Comparing these pubic bones with those of a female (PI. XVI. 

 fig. B. B'.), we find the latter not deviating from the form usual 

 in other species of Leuciscus : namely, each of them has more the 

 appearance of a single bone, with a longitudinal ridge and with 

 a deep and wide notch in front ; they are more parallel to one 

 another or slightly convergent. In specimens of the same size, 

 the pubic bone of the male is 1^ as broad as that of the female. 

 The point where the first two rays articulate is not much 

 thickened, and these rays themselves ai-e only half as stout as 

 in the male. The posterior processes of the pubic bones are 

 similarly shaped, but only. half as large ; and their broadest side 

 has a horizontal direction. 



Prof. Troschel* described and figured, in the same year in 

 which I published the observation on the externally visible 

 sexual difference of the Tench, one of those remarkably well- 

 preserved freshwater fishes from the Braunkohle of the Sieben- 

 gebirge. He found therein the same structure of one of the 

 rays of the ventral fins and the broad pubic bones; and not 

 being aware of the peculiarity of this part in the Tench, he called 

 the fish Leuciscus tarsiger, or Tarsichthys elegans. I think the 

 specimens on which this species is founded are males of a species 

 of Tinea. Leuciscus macrurus, Agass., certainly is a different 

 species, and not the female of Tarsichthys, having much larger 

 scales, similar in size to those of Leuciscus vulgaris. But Tars- 

 ichthys elegans agrees, moreover, in other respects with Tinea, 

 Most of the European Leucisci have nine rays in the ventral 

 fins, whilst Tinea vulgaris, like Tarsichthys, has ten, or, in fact, 

 * Verhancl. Niederrhein. Vereins, xi. pi. 1. f. 2, 3. 



