8 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59. 



/Sjjecific characters of male. — This is the first male of the species 

 to be recorded and may be compared with the male of Achtheinus 

 'pinguis described on page 236 of volume 42 of these Proceedings. 



Carapace horseshoe-shaped, three-sevenths of the entire length and 

 as wide as long, not including the posterior lobes. Frontal plates 

 well defined, narrowed to a point on the median line, but wide at 

 the lateral margins, where each projects in a rounded lobe over the 

 basal joint of the antenna. Lateral areas narrow, with the trans- 

 verse groove about in the center. Posterior lobes narrow but long, 

 almost reaching the posterior margin of the third segment. Eyes 

 fused on the median line. 



Second and third segments fused, the narrow lobes at the posterior 

 corners of the second segment reaching back nearly to the fourth 

 segment. The latter segment is about half the width of the carapace 

 and is much narrowed anteriorly where it joins the third segment, 

 with a slight notch on the posterior margin on either side of the mid- 

 line and some distance from it. Genital segment barrel-shaped, the 

 posterior corners prominent, and each armed with a single large 

 spine. Abdomen short, triangular, and one-jointed; anal laminae 

 scarcely projecting beyond the tip of the abdomen, each armed with 

 four long plumose setae and a short basal spine on the outer margin. 



Of the appendages the second antennae are slender and strongly 

 curved, and lack the row of teeth found in the female. The mouth 

 tube is very long and narrow; the maxillae at its base are slender 

 and each is tipped with a long spine. Each maxilliped has but a 

 single claw, much longer than in the female, but shutting down 

 similarly against a pad. 



Color (preserved material) a uniform cinnamon brown, lighter 

 and yellowish in the thinner portions of the carapace. 



Total length, 3 mm. Carapace, including the posterior lobes, 2 

 mm. long., 1.40 mm. wide; genital segment, 0.55 mm. long, and the 

 same width. 



Remarks. — This male shows a marked similarity to that of pinguis 

 described in the reference given above. It may be distinguished by 

 the fused eyes, the long spines at the posterior corners of the genital 

 segment, the long and narrow mouth tube, and the presence of but 

 a single claw on each maxilliped. This last character shows that 

 the presence of two claws on the maxillipeds, shutting past each other 

 like the blades of a pair of scissors, must be regarded as a specific 

 character of pinguis and not as a character common to the genus. 



The two hosts here recorded are new for the genus, as well as the 

 species, and it may be added that a single female specimen of the 

 present species was obtained from another new host, the cow shark, 

 Notorhynchus maculatus on the California coast in 1911, and has 

 been given Cat. No. 42274, U.S.N.M. 



