248 REPORT OF NEW JERSEY STATE MUSEUM. 



fifth one, with a lateral irregular pigment cell. Caudal segment 

 round, with a pair of divergent appendages. Length (1% lines) 

 2.3 mm. (Leidy. ) 



Remarks. — Known only from Atlantic City, where it was dis- 

 covered by Dr. Joseph Leidy in 1855. He says it is not a very 

 abundant parasite, and after having accidentally found a speci- 

 men, fifty fiddler crabs were destroyed in a search for other 

 examples, without any more having been found. The parasite 

 produces no deformity, visible externally, of the animal it infests. 

 The male was found in the embrace of the female. So far it 

 seems to occur only in the fiddler crab, Uca pugilator. 



Super-Family IDOTHEOIDEA. 



Uropoda lateral, valve-like, ventrally placed, closing over five 

 pairs of branchial pleopoda attached on outer edges to sides of 

 terminal segment and opening and closing like folding doors. 

 Legs of first pair not cheliform. 



These animals differ from all the known isopods in the above 

 characters. Three families are generally admitted, though but 

 one represented in New Jersey. 



Family IDOTHEID.E 



Body more or less depressed, with segments of mesosome of 

 uniform appearance, coxal plates sometimes distinctly defined, 

 sometimes confluent with segments. Metasome with some or all 

 segments consolidated to form large terminal piece, carrying 

 normal number of pleopoda. Superior antennae comparatively 

 small, with flagellum uniarticulate. Inferior antennae more or 

 less elongated, originate outside superior from lateral corners 

 •of cephalon. Oral parts mostly normal, though no mandibular 

 palps, and joints of maxillipeds often reduced in number. Legs 

 rather strongly built, increasing in length posteriorly, three an- 

 terior pairs sometimes subcheliform. Anterior pairs of pleopoda 

 Avith densely setiferous rami, second pair in male with usual 

 stylet. Uropoda very large, lamellar, valve-like, closing over 



