Prof. Owen's Description of the Lepidosiren annectens. 355 
want the pancreatic ceca, the analogy which Lepidosiren offers to one genus 
in that group, Belone, in the elongated slender form of the body and its green 
bones, is not without interest. 
In the low condition to which the pectoral and ventral fins are reduced, 
the zoologist who deals merely with external characters would see in the 
Lepidosiren a transitional form between the abdominal and apodal groups of 
the Malacopterygii. But by far the most important affinities which a deeper 
research into the organization of the Lepidosiren brings to light, are those to 
the higher Cartilaginous Fishes which are indicated by the semiossified con- 
dition of its skeleton ; by the removal of the acoustic labyrinth from the cavity 
into the parietes of the skull ; by the number of branchial arches ; by the sim- 
plicity of the maxillary apparatus ; by the spiral intestinal valve ; and, above 
all, by the condition of the oviducts as distinct tubes with two separate, aper- 
tures. 
From every group of Fishes, however, the Lepidosiren is sufficiently distinct 
to form the type not merely of a genus, but of a family; and, in the natural 
system, it forms a link connecting the higher Cartilaginous Fishes with the 
Sauroid genera Polypterus and Lepidosteus ; and at the same time makes the 
nearest approach in the class of Fishes to the Perennibranchiate Reptiles. 
EXPLANATION OF THE PLATES. 
Tas. XXIII. 
External Form and Skeleton of the Lepidosiren annectens, on the scale of 
8 inches to a foot. 
Fig. 1. Side view of Lepidosiren annectens. 
2. Upper view of the same, in outline. 
a. Filamentary anterior extremities, or pectoral fins. 
b. posterior extremities, or ventral fins. 
3. Transverse section of the same, one inch in advance of the ventral 
filaments. 
