PISCES. 205 



found also on the east coast of South Africa in the morasses of Quellimane. 

 PETERS saw specimens 2' long; from the Gambia none are known that 

 were much longer than i'. External gill-leaflets above the gill-aperture 

 occur in Lepidosiren annectens from the Gambia (at least sometimes) as well 

 as in the fish from Mozambique. In one specimen I saw two on the left 

 side whilst on the right side they were wanting; PETEES gives three 

 on each side to the fish observed by him. The inferior margin of the awl- 

 shaped fins has a membranous border with fine rays, which OWEN has not 

 noticed, but which in the specimen from the Gambia observed by me was 

 not absent, although it was much smaller than that recorded by PETEBS in 

 the fish from Mozambique. In Lepidosiren paradoxa, which I know only 

 from figures, the border appears to be absent; external gills were not 

 observed either by BISCHOFF or by HYBTL. 



In the internal structure of Lepidosiren paradoxa and Lepidosiren 

 annectens there is some difference, but considering the great agreement 

 of these two species I think it unseasonable to adopt a separate genus for 

 each of them. Perhaps also much of the difference may disappear on 

 closer comparative investigation. 



When the morasses or brooks, in which these animals live, have lost their 

 water in the dry season, these fishes keep at the depth of some feet under- 

 ground. They live on vegetable matters, as the Brasilians report, and as 

 indeed is apparent from microscopic investigation of the remains of the food 

 in the intestinal canal. 



The branchial arches are cartilaginous strips without connexion with the 

 hyo'id bone ; the African species has six on each side, the American five. 

 These arches however do not all bear gills ; only on two arches (on the 

 third and fourth, or in the African species on the fourth and fifth) is there 

 a double row of gill-leaflets present. On each side there are three or four 

 arterial arches which arise from the bulbus arteriosus ; branches alone 

 of these go to the gills. Perhaps at an earlier period of life the gills are 

 more developed and are present on all the branchial arches, as HYBTL sur- 

 mises ; but in the adult animal the change from venous to arterial blood is 

 chiefly effected in the swimming-bladder; this forms two large cellular sacs 

 under the back, behind the peritoneum, and has in front a common part 

 which bends round the oesophagus below and opens with a short canal on the 

 abdominal surface, not in the middle, but somewhat towards the right side, 

 by a fissure (glottis) into the oesophagus. The vein of the swimming- 

 bladder, the pulmonary vein, enters the auricle of the heart separately, 

 at a distance from the vence cavce. In Lepidosiren paradoxa the auricle is 

 double ; the partition however is not a continuous membrane, but a reti- 

 form tissue everywhere perforated. 



The urinary bladder is situated and opens behind the rectum. This is a 

 piscine conformation. The stomach is little wider than the oesophagus, 

 which passes into it without any definite boundary. At the pylorus there 

 is an annular membranous valve near which the gall-duct opens. The 

 intestinal canal has a spiral valve (as in many Plagiostomes), which 

 terminates at some distance from the extremity. The anus is not situated 

 in the middle, but sometimes more to the right (commonly so in Lepido- 

 siren annectens), sometimes more to the left. 



