1890.] MR. O. THOMAS ON MAMMALS FROM VERA CRUZ. 71 



the egg, the fish-like larva does not acquire any external gills, but 

 opercular folds are distinctly visible and water taken in by the 

 tnoutK is expelled by these branchial clefts. On the third day, the 

 head broadens, flattens ; the eyes become large and prominent ; the 

 nostrils assume a dorsal position ; the gape of the mouth increases 

 in width and two long maxillary barbels rapidly appear near the 

 angles of the mouth, and soon grow into long feelers which give the 

 advanced larva its well-known Siluroid appearance. Neither in the 

 embryo nor in the tadpole are any teeth or horny plates developed in 

 the jaws ; nor are there any special papillae surrounding the mouth. 

 I have prepared and forwarded some ova and early larvae to Dr. 

 Schauinsland, of Bremen, who proposes to investigate the develop- 

 ment. 



Xenopus Icevis, unlike most frogs and toads, does not produce any 

 croaking, but has during the breeding-season a peculiar dull tick-tick 

 note, almost inaudible at three feet distance, ■which it produces 

 under water. I have satisfied myself, by dissections, that the 

 sound is produced by friction of the glottis against the borders of 

 the (median) eustachian opening, the air being at the same time 

 carried from the lungs into the buccal cavity, and vice versd^. 



5. On a Collection of Mammals from Central Vera Cruz, 

 Mexico. By Oldfield Thomas, F.Z.S., Natural History 

 Museum. 



[Eeceived January 14, 1890.] 

 (Plates VI. & VII.) 



During the years 1887 and 1888 a large number of zoological 

 specimens were collected in the Province of Vera Cruz by a scientific 

 expedition organized by the authorities of the Mexican Museum, 

 under the superintendence of Dr. F. Ferrari Perez, Director of that 

 Institution. Thanks to the kind intervention of Messrs. F. D. 

 Godman and O. Salvin the Mammals then obtained have been 

 entrusted to me for determination, and a duplicate set of them 

 acquired by exchange for the Natural History Museum. 



The collection consists of about 100 mammals, belonging to 21 

 species, and a complete list of them is given below. 



The importance of this series lies in the fact that every specimen 

 has been properly labelled with its exact locality and date, and in 

 many instances with its native name and the colour of its eyes, all 

 of these particulars being too commonly neglected in the case of 

 mammals by the very collectors who would insert them most care- 

 fully on the labels of birds. 



^ [Six examples of Xenopus Iwvis have just been received alive by the Society 

 from their excellent correspondent the Rev. G. H. R. Fisk. They were obtained 

 at Rondebosch, near Capetown. — P. L. S.] 



