606 MR. E. B. POULTON ON THE [DcC. 1 8, 



The ring of secondary papillse is less regular in Halmaturus than 

 in Perameles &c., and it is common to find single papillse within the 

 ring {i.h.p., fig. xxviii. Plate LV.)- Between the coronate papillae 

 isolated hair-like papillae are common, rising singly from the epithe- 

 lium. In all respects these resemble the hair-like papillse of the 

 coronate rings. (They are shown in fig. xxviii. Plate LV., s.h.p., and 

 in vertical section in fig. xxvii. Plate LV., s.h.p.') These isolated 

 slender papillae with no tendency to coalesce into rings are very 

 characteristic in tongues which in other respects also show traces 

 of more primitive affinities than those of other Marsupials. (The 

 posterior part of the tongue of Ornithorhynchus is covered with 

 closely set single hair-like papillae, very much resembling the 

 papillae here described, and agreeing in the important point that 

 each hair-like papilla possesses but a simple papillary upgrowth.) 

 The coronate papillae are of large size, and there are only about 10 

 to the square milHmetre close to the posterior circunivallate papilla. 

 A little anteriorly (by the anterior circumvallate papillae) they 

 become rather smaller, and I counted 12 to the square millimetre. 



Li ascending from the smooth to the papillate surface, the long 

 papillary processes of the former first bear simple papillae ; these 

 form an irregular row (one or two deep, and sometimes absent) and 

 then coalesce into the coronate papillae. There are a few of these 

 simple papillge, bent upwards so as to be almost parallel with the 

 surface of the tongue, below the lateral organ in some sections. 

 The coronate secondary papillae curve upwards from the sides 

 towards the middle of the tongue (see fig. xxix. Plate LV.) ; but 

 this is not so marked as in Phalangista, at any rate in the posterior 

 part of the tongue. The secondary papillae of the upper surface are 

 curved backwards ; but this is very slightly marked posteriorly, 

 where the coronate papillae are tall and slender ; while anteriorly (in 

 the piece of tongue in my possession) they become shorter, stouter, 

 and the hair-like secondary papillae much recurved (see fig. xxvii. 

 Plate L v.). The epithelium is immensely thickened in passing from 

 the smooth into the papillate region (see fig. xxxi. Plate LV., 

 s.e., where the transition is taking place, and compare the thickness 

 with the less magnified fig. xxvii. Plate LV., which is taken in the 

 middle line of the papillate surface). Although the epithelium 

 changes in thickness, the four layers of the complex epithelium can be 

 detected in it and enter into the coronate papillae. This is best shown 

 near the transition. (See fig. xxix. Plate LV., which represents dia- 

 grammatically the arrangement of the four layers in a single coronate 

 papilla close to and above the lateral organ. The section is of 

 course vertical and transverse, and the curve of the secondary 

 papillary processes is upwards. The layers correspond to those in 

 fig. xxxi. Plate LV. In other parts of the papillate surface the 

 distribution of the corneous layer (2) would be more symmetrical 

 upon the secondary papillae.) We thus have a proof that the layer 

 (2) previously described is truly corneous, inasmuch as in these fine 

 processes, of mechanical use, it rises to the surface and is confined to 

 the effective side, or both sides where both are effective. The very 



