414 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxiii. 



frontal plates. In the second pair the middle joint is considerably 

 swollen, while the terminal claw is rather slender and weak. There 

 is only one pair of adhesion pads, situated just behind the bases of 

 the first antennae and close to the edge of the carapace. The pair 

 that usually accompanies the second antennae have degenerated into 

 minute disks, too small to be of any service for prehension. 



The mouth-tube and second maxillae are similar to those in the 

 male of sinuatus; the first maxillipeds are stout, both joints consid- 

 erably swollen, the terminal claw straight and more than twice the 

 length of the secondary one. The second pair are also much swollen, 

 and are armed with a strong forceps made of two stout knobs whose 

 inner surfaces are flattened where they come together. The arrange- 

 ment of the spines and setae on the swimming legs is as follows : First 

 exopod, 1,0; 4, III: endopod, 0, 0; 0, III: second exopod, 1, I; 4, IV: 

 endopod, 0, I; 0, VIII: third exopod, 1, I; 4, V: endopod, 0, I; 0, V: 

 fourth exopod, 1, 0; 4, V: endopod, 0, I; 0, IV. 



Total length, 7.57 mm.; length of carapace to tips of lateral lobes, 

 4.43 mm. ; width of same, 4.23 mm. ; length of free segment, 2 mm. ; 

 length of genital segment, 1.4 mm. 



Color (preserved material) a uniform yellowish brown without pig- 

 ment markings. 



This species was established by Rathbun in 1886 upon two speci- 

 mens taken from a dusky shark, CarcJiarhinus ohscurus, Cat. No. 

 6198, U.S.N.M. Another specimen. Cat. No. 8119, U.S.N.M., was 

 found upon an undetermined shark, taken in Vineyard Sound, and 

 four specimens, Cat. No. 6022, U.S.N.M., upon a sand shark, Car- 

 charias littoralis, from the same locality. Since the publication of 

 the species five other lots have been secured; two of these, were 

 obtained from sand sharks at Woods Hole; one, Cat. No. 32734, 

 U.S.N.M., includes five young females in different stages of devel- 

 opment; the other, Cat. No. 32732, U.S.N.M., includes a single 

 male which is made the type of the species. Another lot. Cat. 

 No. 6195, U.S.N.M., containing two females was found on Atwood's 

 shark, Carcharodon carcharias; a second lot of three females, Cat. 

 No. 11614, U.S.N.M., was found on a "Gray" shark in Vineyard 

 Sound; a tliird lot of four females, Cat. No. 32754, U.S.N.M., from 

 the back of a small shark (species not given) taken in the Gulf of 

 Mexico. 



The chief variation in these specimens is in the amount of pigment 

 on the carapace and dorsal plates and in the relative size of the third 

 pair of plates; similar variations are found in all pigmented species. 



