20 



PEOr. B. EAT LANKESTEE ON LEPIDOSIEEN AND PEOTOPTEEUS. 



from the Gambia district, West Africa, and had been living two years in the 

 Society's Gardens. 

 Fig. 3. Left hind limb of the specimen of Lepidosiren drawn in fig. 1, reflected forward 



•which is as it were cut oflF above and below bo as to form a strong median angle (Plate II. figs. 5 & 6). The 

 line separating the stronger sculptured part of the scale from the smooth softer piece presents a fine curvature 

 .(a a in figs. 5 & 6 of the Plate). In old spirit-specimens of Protoptems (woodcut, fig. 2) and also in similar 



Pig. 1. 



'.- ■■/■ .; \ s ' 'v -.^ ■. ■; . .- 



Pig. 2. 



M^'i^^^M/Mi-^im 



9: pott. 



aiitX^ 



]JOSt. 



Diagram of the lozenge-shaped areae outlined by pigment- 

 cells (which are also seen scattered and in some places 

 aggregated on the general surface), from the mid-body 

 region of Profopterus anncctens, as seen in a freshly- 

 preserved specimen (six months in spirit). 



Pig. 3. 



Diagram of the same arese as those drawn in fig. 1, as 

 seen in a specimen which has been long preserved in 

 weak spirit. The pigment has become altered in colour 

 (from blue-black to a warm brown) and has diffused 

 into and stained adjacent tissue. The subepidermic 

 connectiTe tissue is wrinkled and semitransparent, and 

 permits one to see the outhne of the semicircular curve 

 (a, a) which separates the sculptured from the unsculp- 

 tured portion of the subjacent scale. 



specimens of Lepidosiren, this curved line shows through the softened and wrinkled dermis (woodcut, fig. 2, a a) 

 owing to the greater thickness and differentiated texture of the sculptured portion of the buried scale. 



The relation of an entire scale to the lozenge-shaped 

 pigment-area of the surface-tissues is shown in woodcut 

 fig. 3, where the scale is drawn so as to show its sculp- 

 tured and unsculptured portions, and the supeijaeent 

 lozenge-area of pigment-cells is dotted in. 



In the figures 5 and 6 of Plate II. the dotted line 

 indicates similarly the anterior border of a superjacent 

 pigment-lozenge. 



If we now compare the figure of the scale of Cera- 

 todus forsteri (PI. II. fig. 4) with the diagrams and 

 drawings of the scales of Protopterus and Lepidosiren, 

 it becomes apparent that there is here also a smooth 

 unsculptured posterior portion of the scale. In Cera- 

 iodtts, however, this part of the scale is firm and thick, 

 and is freely exposed, covered neither by dermis nor 

 epidermic epithelium. 

 The most probable interpretation of these facts, from the point of view of the ancestral history of the scale 



Diagram to show the relation of the scale of Prntopterus 

 to the superjacent lozenge-shaped area outlined by 

 pigment-cells, a, the line separating the thicker 

 sculptured portion of the scale from the softer and 

 smooth, pointed portion, c ; b, the position of the 

 pigment-ceUs disposed in the form of a lozenge. 



