PEOr. E. EAT LANKESTEE ON LEPIDOSIEEN AND PEOTOPTBEUS. 19 



5 inches long the pectoral fins may have a length of 3i inches. Apparently the fins 

 are continually being shortened by violence or disease, and continually grow again, not 

 to the relative length seen in the young, but so as to repair to a great extent the loss. 

 Hence it seems that little importance can be attached, in the diagnosis of Protopterus 

 and Lepidosiren, to the relative length of the fins, unless a very large series of each 

 is studied. 



I am also unwilling to attach much importance to the general form of the head and 

 the relative position of the eye in relation to the angle of the mouth as specific or 

 generic characters, since we have no drawing or record of freshly killed or living 

 specimens of Lepidosiren, while preservation in spirit is liable to be attended by 

 considerable distortion of the head. 



But it is fairly apparent, as shown in the Plate, that the head of Protoptenis is less 

 blunt anteriorly than that of Lepidosiren, and that the eye of Lepidosiren is placed 

 much further forward than that of Protopterus, so as to be in front of the angle of 

 the mouth. 



EXPLANATION OF PLATE II. 



Fig. 1. Lepidosiren from the swamps of the Chaco (Upper Paraguay River), natural 

 size : male. Drawn from a spirit-preserved specimen in the Oxford University 

 Museum by J. Bayzand *. 



Fig. 2. Protopterus annectens, Owen. Drawn by J. Bayzand* from a specimen recently 

 killed and untouched by alcohol. The specimen is a female, was brought 



* Sv'ote, Dec. 20, 1895. — It is only fair to the artist, Mr. Bayzand, to point out that a curious inaccuracy has 

 crept into the Uthographio reproduction of his drawing which is not present in the original as made by him. 

 It will be observed, in the two large figures of Lepidosiren and Protopterus respectively, that there is a 

 marking on the surface of the body, especially strongly rendered in the drawing of Protopterus, which 

 appears to indicate "scales," and was interpreted as such by the lithographer. As a matter of fact, no scales 

 at all or -parts of scales are visible on the surface of the body of a fresh or well-preserved specimen of Proto- 

 pterus. Tho scales are entirely overlaid, in both Protopteras and Lepidosiren, by soft vascular connective tissue 

 in addition to a weU-developed epithelium. The areoe which are marked out on the surface of the body and 

 have been wrongly rendered in the lithograph as scales are in reality lozenge-shaped areas outlined by the 

 greater abundance along their margins of the large branching pigment-cells of the connective tissue which 

 overlies as a uniform and continuously flat layer the subjacent scales. The lithographer, thinking he was 

 called upon to represent protruding imbricated scales, such as appear on the surface in many common 

 Teleostean fishes, has changed the outline of the pigment-arese and represented the posterior border as a portion 

 of a circular curve, a form which it does not present either in Protopterus or Lepidosiren, and which, was not 

 given to it in Mr. Bayzand's original drawing. The true form of these ares delimited by pigment-cells is 

 seen in the woodcut, fig. 1. The areae are seen to have a pointed angular posterior border, and not a curved 

 one. The anterior border, on the contrary, shows a rounding-off of the angle, so that the form of the markings 

 given in the lithograph should be reversed. The area: are less elongated near the head and near the origin of 

 the median fins than in other regions. 



Though these areas are in no way to be regarded as scales, they yet correspond in position and number with 

 the subjacent imbricated scales. Each scale in Protopterus and Lepidosiren has a large soulptiu-ed area carrying 

 the denticulations figured in the Plate, and, extending posteriorly beyond this, a softer unsculptured portion 



d2 



