76 G. A. MacCırrum, 
In the course of examining many fish of various sorts, worms 
belonging to the genus Microcotyle were found attached to the gills 
of the Black angel fish (Pomocanthus arcuatus), the Butterfly fish 
(Chaetodon ocellatus), the small Butterfly fish (Chaetodon capistratus), 
the Grass porgy (Calamus arctifrons), the Pork fish (Anisotremus 
virginicus), the Yellow finned grouper (Epinephalus flavolimbatus), and 
the Spanish hogfish (Harpe rufa). These are so much alike that I 
hesitate to describe them as separate species and even in describing 
them under one name would point out the remarkable similarities 
which exist between them and M. caudata, sebastes, elegans and 
even stenotomi of Gorto. It is true that these four species of 
Goro differ among themselves sliehtly in size, in the number of 
suckers and in the number of testes but otherwise they are 
remarkably alike. Furthermore it is clear from the study of 
immature forms that the size, number of suckers and number of 
testes increase with age. Naturally one might suppose that if the 
worms are quite mature a constant number would be attained but 
it is common enough to find worms of various sizes and ages upon 
the gills of the same fish and difficult to decide which of these is 
quite mature. Therefore such numbers seem hardly acceptable as 
criteria of specific differences and are not to be compared in im- 
portance with the marked differences in form of the suckers, 
genital armature etc. which form the basis for most cases of specific 
differentiation. 
For that reason it is with the idea of a later and more careful 
revision of this whole group and because the forms do not correspond 
very closely with Goro’s that they are described together under one 
specific name. 
All of these worms are about 3,5—4,5 mm X. 0,6—0,7 mm in 
size with a sucker disc which curves up backward and is furnished 
with fifty to seventy-five suckers ranged along the ventral margin 
and projecting laterally on short stalks. These suckers have a rather 
delicate chitinous skeleton of the form shown in. the drawing with 
short lateral spur and are uniform in character. 
The mouth suckers are unarmed and obliquely placed at the 
sides of the mouth. They are divided by a partition. The mouth 
is slightly subterminal with an overhanging lip. The pharynx is 
well developed and leads into a rather short gesonhanus which bi- 
furcates into the lateral intestinal coeca. 
Just behind the bifurcation is the armed genital opening. In 
