Miscellaneous. 
243 
P. gracilis, nigricans, lateribiis parallelis, postero acuto abrupte, ple- 
rumque antico recto ; oculis duobus. Long. 9 lin., lat. 1 lin. Habi- 
tat in fontibus Pennsylvaniae. 
Description. Oblong, limaciform, naked, convex superiorly, flat in- 
feriorly, very contractile ; sides ordinarily parallel, convex when the 
animal is in a contracted state, convergent anteriorly when elon- 
gated ; anterior extremity with a lateral triangular auricular appen- 
dage, straight in front, by contraction becoming convex or concave ; 
posterior extremity abruptly pointed ; ocelli two, anterior, composed 
of an oblong, semitransparent (nervous ?) mass with an intensely 
black dot of pigmentum at the internal posterior part ; ventral aper- 
tures two ; oral aperture a little less than one-third the length of the 
body from the posterior extremity, and very dilatable ; generative 
aperture half-way between the oral aperture and posterior extremity. 
Colour black or iron gray, and in some younger specimens lateri- 
ceous. 
This animal I have only found in abundance in the neighbourhood 
of Prof. Haldeman’s residence, near Columbia, Pa. In a spring in 
front of his house, thousands of them may be seen gliding along the 
bottom ; some of them occasionally creep up the sides to the surface 
of the water, turn upon the back, and by making the ventral surface 
concave, float about in the manner of the Limniad(B. It appears to 
be carnivorous in habit, or at least it attaches itself to animal matter 
dead or living, in preference to vegetable matter. When irritated, 
it throws out a considerable quantity of very tenacious mucus. 
In structure it appears to be intermediate between the entozoic 
Distomata and the annulose Hirudince. I could not detect any trace 
of annulation, but I think that this alone would hardly be sufficient 
to place it lower than the latter animals, because, in a closely 
allied animal, the Gordius aquations, although there is no annulation 
in the perfect animal, yet in the embryo state I find it to exist. 
The whole animal is composed of a delicate granular structure ; 
the only approach to muscular fibre is in the longitudinal striation of 
the integument rendered more distinct by the pigmentum nigrum, a 
radiated appearance around the oral orifice, and a faint transverse 
and longitudinal arrangement of the granules entering into the com- 
position of the proboscides, seen more or less distinctly in the con- 
tinued movement of these organs when slightly compressed beneath 
the microscope. 
The digestive cavity presents the same dendritic arrangement as 
in PlanaricB generally*, but instead of possessing a single sucker or 
proboscis, the full-grown animal has not less than twenty-three ; 
varying however in this respect from three upwards, according to the 
age of the animal. One of these proboscides joins the digestive cavity 
at the posterior part of the anterior division, as usual ; the others join 
the remaining two divisions at their internal side in their course 
backwards. They are considerably longer, but narrower, than in P. 
lactea\, and when not in use are closely packed together within the 
Duges, Ann. Sc. Nat. 
f lb. 
16* 
