PEOF. B. EAT LAJSfKBSTEE ON LEPIDOSIEEN AND PROTOPTEEUS. 



15 



and the description given by Natterer of the South-American Lepidosiren. He especially 

 drew attention to the relative distance (and number of vertebrae) intervening in the 

 two species between the anterior and posterior limbs. The difference thus indicated 

 is very striking, and is expressed in general terms by saying that Lepidosiren is long 

 and eel-like, whilst Protopterus is comparatively short and thick-set. 



In order to place the distinction on a definite numerical footing, it is found convenient 

 to take the following points of measurement : —A. Total length from the extremity of 

 the snout to the extremity of the caudal fin ; B. From the extremity of the snout to 

 the anterior margin of the pectoral fin where it springs from the body ; C. From the 

 anterior margin of the pectoral fin to the anterior margin of the pelvic fin ; D. From 

 the anterior margin of the pelvic fin to the extremity of the tail ; E. From the anterior 

 margin of the pectoral fin to the vertical drawn from the anterior limit of the dorsal fin. 



In the following lists I give these measurements, A, B, C, D, E, for five specimens 

 of the Paraguay Lepidosiren, and for six specimens of Protopterus. It is no doubt true 

 that the ratio of these lengths one to another differs in larger specimens as compared 

 with quite small specimens ; also that the distortion caused by stufiing may entirely 

 obscure the natural proportions. With the exception of two large stuffed specimens 

 of Protopterus in the British Museum, all the specimens, the measurements of which 

 are here recorded, were preserved in alcohol. 



If we take the length of B (from tip of snout to anterior margin of pectoral fin) as a 

 unit, these measurements may be expressed in a form facilitating a direct comparison 

 of all the specimens examined. 



It will facilitate the statement of these results if we call A the total length, B the 

 head-length, C the inter-membral length, D the post-pelvic length, and E the cervico- 

 dorsal length. If we give the total length in centimeters it will be unnecessary to 

 burden the reader with the other measurements in centimeters ; it will be sufficient 

 to give them in terms of the unit of comparison adopted, viz. the head-length. 



Table A. — Measurements o/" Lepidosiren /rom Paraguay. 



