ON ARHYNCHUS HEMIGNATHI. 207 
On Arhynchus hemignathi, a new Genus of 
Acanthocephala, 
By 
Arthur E. Shipley, 
Fellow and Tutor of Christ’s College, Cambridge, and University Lecturer in 
the Advanced Morphology of the Invertebrata, 
With Plate 12. 
ANATOMY. 
In the summer of 1894 I received from Mr. Perkins, of Jesus 
College, Oxford, seven small parasites which he had noticed ad- 
hering lightly to the skin around the anus of a species of bird, 
Hemignathus procerus, which he collected in the island of 
Kauai, one of the Sandwich Island group. Each of these para- 
sites was divided into three regions,—a head, a collar, and a 
trunk ; and, in fact, they have an almost ludicrous resemblance 
to a young Balanoglossus with one or two gill-slits (figs. 1, 11, 
and 111). On investigating their anatomy it at once became 
evident that the animals belonged to the group Acantho- 
cephala, and, further, that they differed from the other 
members of the group in the absence of what is perhaps their 
most characteristic organ,—from which, indeed, they take their 
name—the hooked proboscis or introvert. ‘The absence of so 
characteristic a structure, and the fact that the parasites were 
found outside the body, i.e. not as an endoparasite, but as an 
ectoparasite, lightly attached to the skin, made me think that 
perhaps the hooked introvert had been left behind in the in- 
testine of the host, and that the body of the parasite had passed 
out of the alimentary canal of the bird. However, careful 
inspection failed to reveal any trace of a scar or mark where 
the introvert might have been broken off; and although in 
