1894.] ON THE ANATOMY OP ATHEEUBA AFEICANA. 675 



" that the gill-membranes are united to the isthmus, not forming 

 a fold across it." But this character is not always constant. The 

 museum of Christiania has three specimens of A. acipenserinus, 

 received through the kindness of Dr. G-ilbert from the Stanford 

 University, Cal. In two of these the gill-membranes form a 

 short but distinct fold across the isthmus ; in the third it is hardly 

 perceptible. In A. gilherti some of the specimens show a trace of 

 a similar fold, whilst in others the isthmus is smooth. 



A. decagonus, Bl. Schn. 1801, forms another transitional stage 

 between the last group and the other, in which the gill-membranes 

 form a distinct fold across the isthmus (as in A. cataphractus). In 

 the first species the fold is always present, but very short. 



Consequently Podothecus can hardly rank as a genus, but forms 

 in the typical genus Agonus a group of species which, by the 

 structure of the snout and the dentition, may be separated from all 

 Agonidce. 



Christiania, Oct. 1894. 



5. On the Anatomy of Atherura africana compared with 

 that of other Porcupines. By F. G. Parsons, F.R.C.S., 

 F.Z.S., F.L.S., Lecturer on Comparative Anatomy at 

 St. Thomas's Hospital. 



[EeceiTed October 12, 1894.] 



The specimen of Atherura africana from which the accompanying 

 notes were made was kindly placed at my disposal by Mr. F. E. 

 Beddard, Prosector to the Society. I was induced to make a 

 rather more exhaustive examination of certain parts of it than I 

 otherwise might have done because I hope that some day I may have 

 the chance of dissecting its Eastern relative, Atherura macrura, and 

 of comparing the anatomy of the two. Professor Mivart's account 

 of the anatomy of Erethizon dorsatum was of great value in com- 

 paring Atherura with the Tree-Porcupines ; but I was unable to 

 find a complete account of a dissection of a Ground-Porcupine, 

 and am indebted to Professor Stewart for the gift of a spirit- 

 specimen of a young Eystrix cristata, which I dissected pari passu. 

 I am also indebted to Professor Howes and to Mr. Oldfield 

 Thomas for their kindness in allowing me the use of their osteo- 

 logical collections. 



Osteology. 



The skull of Ailierura has already been described by Gray l and by 

 Giinther 2 . The former gives the chief characteristics of it and 



1 P. Z. S. 1847, p. 104. 



2 P. Z. S. 1876, p. 743. 



45* 



