Coss—WVematodes, mostly Australian and Fiyian. 253 
( Tunbridgensts) is contracted, but in all the others is slightly expanded at the lip- 
region. Two rows of tactile organs, each consisting of six conical innervated papillee, 
surround the mouth,—the outer spreading row being situated on the margin of the 
head, while the inner row closely surrounds the mouth. These papillze are usually of 
uniform size, but sometimes those of one row, usually the inner, are larger than those 
of the other. It is tolerably certain that the number of lips is three, and that each 
lip is two-parted, though this is not an easy thing to demonstrate, owing to the fact 
that the lips are very low and nearly confluent. The mouth-opening is small, the 
length of the passage leading from it to the pharynx being determined by the 
thickness of the lips, which are uncommonly bulky and powerful. Behind the lips 
the pharynx assumes at once its full width, which is tolerably uniform throughout its 
length in most species; in a few, however, the posterior part narrows somewhat 
gradually instead of suddenly. The absolute length of the pharynx varies, speaking 
roughly, from 30, to 604, the smaller species, as a rule, possessing a smaller pharynx, 
but not by any means proportionately smaller. JZ. digzturus, for instance, notwith- 
standing that it is only half as large as AZ. longicaudatus, has a pharynx quite as 
large as that of the latter. In form the pharynx varies between triquetrous and 
hexagonal, usually three and sometimes all of its edges being clearly indicated by 
longitudinal more or less curved chitinous ribs. A dorsal tooth seems always to be 
present, though it is occasionally inconspicuous. It is usually situated near the 
middle of the dorsal side of the pharyngeal cavity and projects forward and inward, 
often so much as to be very conspicuous. A few species possess ventral submedian 
teeth, rivalling the dorsal in size, and placed on a par with it; probably these 
submedian teeth exist in a more or less rudimentary condition in most of the species, 
but have been overlooked and hence left unnoticed by the authors. Portions of the 
chitinous walls of the pharynx are covered with minute teeth or roughnesses, 
resembling sometimes those of a rasp (first noticed by Dujardin) and sometimes those 
of a mill-saw file (first noticed by Biitschli). These rasp-like or file-like roughnesses 
appear to have a definite relation to the form of the pharynx, and to have a definite 
function, namely, to aid in mastication. I have observed that the species possessing 
rasp-like roughnesses have them placed in opposition to the projecting part of the 
dorsal tooth, the areas covered by the minute teeth beginning near the lateral lines 
and extending toward the ventral part of the pharynx, where the teeth seem less 
developed than at the sides ; the dorsal surface of the pharynx near the dorsal tooth 
is quite smooth. The species observed by me possessing plain transverse striations 
resembling the teeth of a mill-saw file, are species in which the dorsal tooth is 
rudimentary and situated near the base of the pharynx, the position of the striations, 
however, being precisely that of the above-described bands of rasp-like teeth ; the 
walls of the pharynx are, moreover, in-this case traversed by certain curved transverse 
ridges of such a complicated nature that even after considerable study of them I can 
