24 Mr. MoNTAGv's Description of several new or rare Animals, 
THALASSINA. 
Body short, mutable: an aperture at each extremity : the mouth 
furnished with a greatly extended lip serving the double pur- 
pose of collecting nourishment, and of progressive motion. 
THALASSINA MUTATORIA. 
AR. V. Fig. 2. 
Lumbricus thalassema. | Gmel. Syst. p. 3084.—Turt. iv. p. 59.— 
Pall. Spicil. Zool. x. p. 8. t. 1 f. 6. 
This animal is ovate-oblong in a quiescent state, and rather 
more than half an inch in length, but sometimes extends to 
more than an inch, and then changes its form by alternately in- 
flating each end: it is furnished with annulations which become 
ridged at the posterior end, where it terminates in a point or 
nipple: it has also longitudinal striz that decussate the annula- 
tions irregularly, giving a squamous appearance: at the anterior 
end the margin of the aperture extends into a very long amor- 
phous appendage, frequently three or four times the length of 
the body, at other times contracted very short, but never receding 
within the mouth: in the former state it is usually flat; in the 
latter the sides fold together and almost form a tube, becoming. 
much scalloped or wrinkled on the margin; and at the base the 
sides unite, forming a sort of funnel to the mouth’: by this im- 
_ plement not only nourishment is collected, but its only progres- 
sive motion is performed : it is in continual action, thrown about 
in all directions in search of food, and occasionally by. fastening it 
to a distant body the animal is drawn forward, or turned to either 
side: at the anterior end immediately behind the long appendage 
are two very minute feelers which are not always protruded. 
The posterior half of the body is of a blueish-gray, the other 
purplish-pink ; the appendage saffron, paler at the extremity. 
This 
