57<i PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



It is not a very lively species, and thus far has a limited number of 

 hosts. The National Museum collection includes several lots of speci- 

 mens taken at different times, but all, with two exceptions, from 

 similar hosts — the sea basses. As the scientific name of the host is not 

 recorded in most of the instances, it can not be determined whether 

 these hosts were all the same species or not. Lot 6155, consisting of 

 ten males and females from the mouth of Centrojpristes striatus, is 

 taken for the types of the new species. There is another lot, 6119, 

 from the mouth of a "sea bass," and six unnumbered lots, all from 

 the mouths of "sea bass" at or near Woods Hole, except a single 

 female from the mouth of a pollock and another from the mouth of a 

 bonito. 



CALIGUS ALIUNCUS, new species. 

 Plate IX. 



Female. — Carapace ellipitical, one-fifth longer than wide. Frontal 

 plates distinct and very wide, not emarginate at the center; frontal 

 margin nearly straight. Lunules large, semicircular, prominent. 

 Posterior sinuses narrow and quite deep, leaving the median lobe 

 nearty two-thirds the entire width; lateral lobes narrow and curved 

 inward. Thoracic area very large, half the length of the carapace 

 and more than two-thirds of the width (fig. 103). 



Free thorax segment transversely linear, nearly as wide as the geni- 

 tal segment, but very short. Genital segment quadrangular, two- 

 fifths as long as the carapace, a little wider than long, with short and 

 blunt posterior lobes. 



Abdomen one-fifth shorter than the genital segment, but more than 

 half as wide, made up of four segments, of which the two end ones 

 are about equal and considerably larger than the middle ones. 



The terminal segment is deeply hollowed on either side posteriorly 

 for the reception of the small, lateral anal laminae. 



These latter are nearly spherical and do not reach beyond the tip of 

 the abdomen; they each carry three long plumose setae posteriori}^ and 

 a much shorter one on the outer margin. 



Egg cases narrow, scarcely more than one-third as wide as the abdo- 

 men; eggs small and numerous. 



The first antennae are a little longer than the frontal plates, the two 

 joints about the same length, but the terminal one very much the nar- 

 . rower. Second antennae short and stout, with a broad terminal claw 

 and no accessory spine. No trace could be found of the first maxillae. 

 Second maxillae stout, broadly triangular, and nearly as long as the 

 mouth tube. 



The latter is broadty U-shaped, a little more than half as wide as 

 long, and abruptly rounded at the tip. 



Furca Y-shaped, the base longer than the branches and considerably 

 constricted; branches thick, blunt, and divergent. 



