602 ox ariiK skull of the LEPiDosiREif. [June 1, 



that in the winter of 1891, during an afternoon walk just outside 

 the walls of Cairo, on the desert side of the town, I came across a 

 large Weasel with a yellow throat, which on my approach ran off 

 and took refuge in a hole in the old city walls." 



Professor T. W. Bridge, F.Z.S., read a memoir on "The. Morph- 

 ology of the Skull in the Paraguayan Lepidosiren and other 

 Dipnoi." 



The first portion of this paper treated in detail of the structure 

 of the skull in one of the specimens of Lepklosiren collected in the 

 region of the Paraguay river by the German traveller Dr. Bohls. 

 In the second portion was included a revision of the cranial structure 

 of Ceratodus and Frotopterus, and a detailed comparison of the two 

 genera with one another and with Lepidosiren. 



As compared with Frotopterus, the most noteworthy distinctive 

 features of the skull of Lepidosiren were stated to be : — 



(ft) The further atrophy of the occipito-periotic portion of the 

 chondrocranium, and the reduction in height and thickness of the 

 tubercular rods which form the connection between the occipito- 

 periotic and ethmo-nasal regions. 



(6) The extension of the antorbital cartilages into the upper labial 

 folds as far forwards as the extremity of the snout. 



(c) The rotation backwards of the axis of the suspensorial carti- 

 lage to a greater extent than in either Frotopterus or Ceratodus : 

 hence it followed that the suspensorium made a more open angle 

 with the fore part of the basicranial axis than was the case withi 

 either of the two last-mentioned genera. 



(d) The greater development of the fronto-parietal bone, which 

 not only completely covered the dorsal surface of the cranium, but 

 also invested the auditory capsules, formed the lateral bony cranial 

 walls of the interorbital region, and, moreover, strengthened each 

 suspensorial cartilage by investing its outer surface nearly as far 

 ventrally as the articular condyle for the lower jaw. 



In comparing the three types the conclusion arrived at was, that 

 the skull of Ceratodus was by far the most generalized and primitive, 

 and further, of the two remaining genera the skull of Lepidosiren 

 represented but a slightly more specialized type than that of Froto- 

 pterus. Briefly, it might be affirmed that if the skull of Ceratodus 

 were taken to represent a relatively early larval stage, those of 

 Frotopterus and Lepidosiren were comparable to two immediately 

 succeeding but much later stages, while, \^ith one or two ex- 

 ceptions, the diiferences between the two latter genera were 

 much the same in nature and extent as those which, for example, 

 characterized the skulls of first and second year frogs. 



The third section of the paper included a brief summary of the 

 present state of our knowledge of the structure of the skull in the 

 fossil Dipnoi, and a compai'ison of it with existing types. On the 

 evidence afforded by the skull alone, it v\as inferred that Ceratodus 

 was the most primitive of known Dipnoi, and that Frotopterus and 

 Lepidosiren were the specialized and direct descendants of some 

 Ceratodus-\\ke ancestor. Of the fossil Dipnoi, Ctcnodus certainly, 



