214 ARTHUR E. SHIPLEY. 
species. Recently, however, Hamann! has pointed out that 
these species present certain differences which enable him to 
divide the group into three families, each with a corresponding 
genus. ‘To these I venture to add a fourth, to include the 
remarkable form above described. This family may, I think, 
be called the Arhynchide, and the new genus Arhynchus, 
which name refers to the absence of the eversible introvert ; 
and, inasmuch as it is convenient in naming a parasite to have 
some indication of its host, I think the specific name may 
be hemignathi. 
If these terms be adopted, the classification of the Acan- 
thocephala will be as follows, the characteristics of each of 
the first three families being taken from Hamann’s papers. 
ACANTHOCEPHALA. 
I. Family EKcuinoruyncuipa. ‘The body is elongated and 
smooth. The introvert sheath has double walls, and the 
introvert is invaginated into it. The nerve ganglion is in the 
introvert sheath, mostly embedded in it and central in posi- 
tion. ‘The hook papille are only covered with chitin at their 
apex, and the hooks have a process below. 
Genus Echinorhynchus, with the characters of the 
family. 
The vast majority of Acanthocephala belong to this family ; 
a few may be mentioned. EH. proteus, found in many fishes 
aud varying in size with its host ; its larval forms inhabit the 
Amphipod Gammarus pulex, and are also found in the body- 
cavity of numerous fresh-water fishes. E.clavula occurs in 
many fishes and in the intestine of a species of Bufo. E. 
angustatus is found also in fishes, with its larval form in the 
Isopod Asellus aquaticus. EK. moniliformis is said to 
attain maturity in the human intestine; its usual host is a 
mouse, and its larval host the larva of a beetle, Blaps mucro- 
nata. KE. porrigens invests the intestine of the rorqual 
and H. strumosus that of a seal. There are many others. 
1 Loe. cit., and ‘ Zool. Anz.,’ Bd. xv, 1892, p. 195. 
