ORDER PARENCHYMATA. 473 
PoLysToMA, Zéder., (or more properly) HEXASTOMA, 
Have the body depressed, smooth, and six cuppers ranged on 
a transverse line, under the posterior edge. Their mouth 
appears to be at the opposite extremity. 
Some have been found in the urinary bladder of frogs, in 
the ovary of the human female, on the gills of some fishes, 
and in the nasal cavity of certain tortoise. (Polyst. integer- 
rimum, Rud., &c.) 
CYCLOCOTYLES, Otto., 
Have eight cuppers forming almost a complete circle under 
the hinder part of the body, which is broad, and supports in 
front a small proboscis. 
But one species is known, very small, taken on the back 
of the Bellone, Cyc. bellones, Ott. Nat. ac Eur. xi. part ii. 
pl nt 2: 
I also approximate to the fasciole, a subgenus which I 
name 
TRISTOMA, Cuww. 
Their body is a broad and flat disk, behind, at its inferior 
face, is a large cartilaginous sucker, which is attached to the 
body only by a short pedicle, and under its anterior edge are 
found two small ones, between which, a little behind, is the 
mouth. In the parenchyma of the body is a ramified circular 
vessel, the nature of which it is difficult to determine. 
A species of an inch and more in breadth, of a lively red- 
colour, Tristoma coccineum, Cuvy., is attached to the gills 
of many fishes of the Mediterranean, such as the sword- 
fish, &c. 
One of the most extraordinary genera of this family is 
that of 
