Lepidoslren articulata/row Paraguay, 5 



covered by the papilla?, and in smaller examples I found that 

 merely a low fringe of them was oresent. The male Lepido- 

 siren paradoxa likewise exhibits these structures, which vary 

 in the extent to which they are developed, just as in Lepido- 

 siren articulata j the leaf-like form of the 'papillae, however, 

 is not so pronounced, and they are more filiform in shape. 

 Since no mention is made of a similar equipment in the case 

 of the posterior appendage of the female of Lepidosiren para- 

 doxa, which was previously examined, we are probably justi- 

 fied in taking it for granted that in the case of this species 

 also a sexual character is herein displayed. 



The unpaired fin-membranes agree in the two species, and 

 are disposed in the manner previously recorded for Lepido- 

 siren paradoxa. 



The distance of the anus from the tip of the snout is nearly 

 the same in the examples measured ; the position of the anus, 

 on the contrary, is strikingly variable. Bischoff and Castelnau 

 figure it as situated upon the left side of the body to the side 

 of the median plane. In the animals before me the anus 

 occupies this position in the case of eleven males of Lepido- 

 siren articulaia, while in twelve males and two females it 

 lies upon the right half of the body. In their figures of 

 Lepidosiren paradoxa, Natterer, Bischoff, and Castelnau show 

 the anus upon the left side of the body in the female, while I 

 met with it lying on the left in three males, and in two 

 others, on the contrary, on the right. The position of the anal 

 opening is consequently variable, and is not to be regarded 

 as of any value for the purposes of specific diagnosis, nor 

 probably even as a sexual character. 



The epidermis of the two species shows a difference which 

 appears to me to be characteristic. In Lepidosiren paradoxa 

 the coat of scales is distinctly visible, and upon the head can 

 be traced right towards the front ; it is remarkable that in the 

 cephalic region the edges of the scales are directed ante- 

 riorly, as has, moreover, been represented by Natterer; towards 

 the ventral side the scales diminish in size. In Lepidosiren 

 articulata the coat of scales is covered, and to an equal degree 

 in the tvyo sexes, by a very much stouter epidermis than in 

 Lepidosiren paradoxa ; the outlines of the individual scales 

 are consequently very much less distinct ; corresponding with 

 the coat of scales the surface of the trunk is covered with 

 more or less regularly intersecting furrows and wrinkles, 

 while the head and also the tail, as well as the unpaired fin- 

 membrane, are perfectly smooth. Specimens were never- 

 theless met with in which the surface of the body was smooth 

 almost throughout. I should be inclined to regard this 



