Lepidosiren articulata /rom Paraguay. 7 



below, and terminates in an anteriorly-directed curve upon 

 the front end of the nasal sac. All of these lines are more or 

 less interrupted. In the centre of the occipital region short 

 transverse lines are seen running at nearly equal distances 

 one behind the other. In each portion of the lateral lines 

 there can be seen with the aid of a lens small white flecks 

 equidistant one from another upon a dark ground ; these are 

 manifestly the nerve-end-structures. The scales which lie 

 upon the lateral lines are not perforated; the line runs in the 

 anterior portion of the integument, from which the free part 

 of the scale penetrates inwards. 



A difference between the two species, which is probably of 

 importance, is presented by the anterior olfactory apertures. 

 In the existing figures showing these in Lepidosiren paradoxa 

 they are represented as transversely oval openings lying close 

 together. This agrees with the condition which I find in the 

 fish considered by me to belong to this species. In Lepido- 

 siren articulata, on the contrary, the anterior nasal apertures 

 are separated by a triangular process, which runs between 

 them from the margin of the upper lip into the cavity of the 

 mouth ; the nasal aperture is circular, and at its anterior 

 margin there is situated a conical papilla. However, I also 

 find a flat papilla in the case of Lepidosiren paradoxa. 



The skull of Lepidosiren articulata exhibits but trifling 

 deviations from the figures given by Bischoff and Hyrtl. I 

 shall give a representation of it later on. The five carti- 

 laginous branchial arches lie freely on each side in the 

 oesophageal wall, without being connected one with another 

 by means of a copula or being joined to the skull ; this con- 

 firms the statements of Hyrtl with regard to the branchial 

 arches of Lepidosiren paradoxa. 



The vertebral column of Lepidosiren articidata possesses 

 fifty-five pairs of ribs, which agrees with the number given 

 by Bischoff for Lepidosiren paradoxa. The end of the 

 vertebral column runs out into a point, with uniform reduction 

 of all parts to form the monocercal tail. The figure which 

 Bischoff has given of the termination of the caudal vertebral 

 column of Lepidosiren paradoxa was very probably derived 

 from an animal which had lost and incompletely regenerated 

 the tip of its tail ; in this manner the abrupt termination of the 

 posterior end of the notochord there represented is explained. 



The results obtained from the study of the skeleton of the 

 limbs are of special importance. The arches in both of the 

 species before me correspond to the figures given of them in 

 the case of Lepidosiren paradoxa. In the specimens which 

 I assign to this species the skeleton of the appendages is like- 



