[ 325 ] 



VII. On the Morphology of the Skull in the. Paraguayan Lepidosiren and in other 

 Bipnoids. By Professor T. W. Bridge, Sc.B., F.Z.S., Mason College, Birmingham. 



Received May 10, 1897, read June 1, 1897. 



[Plates XXVIII. & XXIX.] 



Contents. p a g e 



I. Introduction 325 



II. Description of the Skull of the Paraguayan Lepidosiren 327 



III. Revision and Comparison of the Structure of the Skull in Ceratodus, 



Protopterus, and Lepidosiren 350 



IV. The Structure of the Skull in Fossil Dipnoi 366 



V. References to previous Literature 373 



VI. Explanation of the Plates 375 



I. Introduction. 



J.HE skull which forms the subject of the following description belonged to one of 

 the numerous specimens of Lepidosiren collected by the German traveller Dr. Bohls 

 in the region of the Upper Paraguay River, and brought to Europe in 1894. As to 

 the specific identity of the Paraguayan specimens with the Amazonian Lepidosiren 

 paradoxa, it is at present premature to express a decided opinion, but on the evidence 

 so far available I see no reason to question the probability that the two are referable 

 to the same species. In any case, as Lankester [20] has shown, the distinction which 

 Ehlers [8] has attempted to draw between his Paraguayan species L. articulata and 

 L. paradoxa, as regards the segmentation or non-segmentation of the axial cartilage 

 of the pectoral and pelvic fins, seems to have no foundation in fact. 



In order to facilitate the comparison of my Paraguayan specimen with others 

 obtained from the same region, and with the Lepidosiren paradoxa of the Amazons, 

 the following measurements were made, and are here expressed in terms of the ratios 

 adopted by Lankester [20, p. 15] : — 



Total length in 

 centimetres. 



Head-length 

 unit. 



Ratio of total 

 length. 



Ratio of inter- 

 membral length. 



Ratio of post- 

 pelvic length. 



Ratio of cervico- 

 dorsal length. 



75 



1 



9-2 



4-51 



3-17 



2-7 



vol. xiv. — part v. No. 1. — February, 1898. 



2u 



