OF A GRAND DIVISION. 263 



df .9 'go 



of them do not perform the functions of such organs, and are 

 the remains of gills of a younger state; just such a structure as 

 we may see in the remains of gill-like bodies on the gill-arches 

 in certain salamanders, e. g\, Siren. In its younger stages of 

 growth it has tufts of external gills on each side of the head, 

 like those of the tadpole of frogs and toads, and the permanent 

 ones of certain adult salamanders, such as Siren, Axolotl, and 

 Menobranchus ; but on the other hand they equally resemble those 

 of the embryos of some of the sharks and skates. The heart is 

 not a double cavity as in the bony fishes, but the posterior half 

 is divided into two ; yet as the partition in this case is a mere 

 net-work, the division is not a complete one, but of that sort 

 which obtains among the so-called Reptilian fishes ; and so I 

 might go on to enumerate every character which this singular 

 genus exhibits, without giving one which does not find its 

 counterpart either in fishes or reptiles. There is one character, 

 however, which has determined some naturalists to class the 

 Lepidosiren among fishes, and that is, it has no nostri/s, and on 

 this account Owen decided that it is rather a fish than a reptile ; 

 but in specimens which BischorT examined, the nostrils are 

 present; and therefore the preponderance passes over to the 

 side of reptiles, if Bischoff's opinion is alone to be taken into 

 account. Between the two authorities, however, the difference 

 is so slight as to amount, I suspect, to an individual disparity; 



Fig. 169. Lepidosiren annectens. Owen. \ natural size. From the River 

 Gambia, Africa, go, the gill-opening ; g, the remains of the external tuft of 

 gills of the youngest staae of growth ; f, the anterior, and f l the posterior, flat- 

 tened, lash-like limbs; df, the dorsal fin-like crest; vf, the ventral fin-like keel; 

 /, the row of scales in the trend of the so-called lateral lymphatic canal ; except- 

 ing on the head, the rest of the scales are omitted. Original, from a specimen 

 kindly lent to me by Prof. Jeffries Wyman. 



