NO. 2280. THE NEW COPEPOD FAMILY SPHYRI I DAE— WILSON. 591 



armed posteriorly with a pair of long conical processes tipped with 

 spines ; no abdomen. 



First antennae indistinctly jointed; second pair bipartite at the 

 tip; first maxillae on the sides of the mouth tube; second pair stout 

 and uncinate; maxillipeds alpo stout, their basal joints fused, the 

 terminal joints chelate. 



Internal generic characters of male. — Espohagus in line with the 

 head axis and opening into the anterior end of the stomach on its 

 ventral surface. Stomach passing insensibly into the intestine, 

 which is al3ruptly contracted into a short rectum at the posterior end 

 of the genital segment. Testes in the back of the head opposite the 

 maxillipeds ; sperm ducts running straight back on either side of the 

 intestine and enlarged into rather small spermatoj^ihore receptacles 

 at the posterior end of the genital segment ; no glands visible. 



Type of the genus. — Paeon ferox., new species. 



{Paeon ., a son of Posseidon.) 



Remarlis. — This is a genus of sliark parasites found in the mouth 

 and gill cavity, the head and long neck buried in the tissues of the 

 host, with nothing but the soft trunk, the posterior processes, and 

 the egg strings visible. 



The head of the parasite is usually near the ventral aorta of the 

 host, and the irritation caused by the burrowing forms a well-defined 

 cyst around the copepod's head and neck, which stiffens the tissue 

 and adds considerably to the effectiveness of the attachment. 



The head and neck are tough and leathery and yet soft enough to 

 yield readily to pressure, so that when endeavoring to remove the 

 creature from the cyst the head will often squeeze out of a small 

 cut, apparently all out of shape. But the elasticity of the tissue 

 restores the normal shape perfectly as soon as the pressure is 

 removed. The trunk and posterior appendages are soft and much 

 less elastic, and it is hence A'ery difficult to preserve the animal in its 

 normal form. They must be kept straight and extended in the pre- 

 servative in the same way that cestodes and similar material are han- 

 dled. In water they are capable of considerable motion, writhing 

 about like a worm and coiling and uncoiling their long necks and 

 bodies. By this means they can move about over the bottom of the 

 vessel containing the water and can even raise themseh^es off the 

 bottom to some extent. But they only live from 36 to 48 hours 

 under such conditions, and it is not at all probable that they ever 

 have occasion to use this form of motion under natural conditions. 



KEY TO THE .SPECIES. 



Head obcordate ; neck much wrinkled ; trunk also obcordate, as wide as long, 



versicolor, new species, p. 596. 



Head transversely elliptical; neck rather smooth; trunk much longer than 



wide, squarely truncated posteriorly fcrux, new species, p. 592. 



62055— 20— Proc.N.M.vol.55 39 



