708 PROCEEDINGS OF THE NATIONAL MUSEUM. voi,. xxv. 



Posterior sinus rather narrow, about one-third the leng-th of the 

 carapace, three times as long as wide; lobes well rounded. 



Sucking disks large, about one-fifth the width of the carapace; pos- 

 terior maxillipeds medium with a triangular basal plate armed with 

 three short blunt teeth, and strongly papillated. 



Antennre small and armed with rather weak spines and hooks. The 

 body projects considerabl}'^ beyond the carapace, the thoracic segments 

 being long and wide; the posterior one projects over the abdomen as 

 a well-rounded lobe on either side with a shallow sinus between. 

 Abdomen broad and long, more than one-third the length of the rest 

 of the body, with well-rounded lateral margins. Anal sinus broad 

 triangular, cut to the center, leaving the two lobes sharply pointed 

 and flaring slightly at their tips; papillfB small and basal. Swimming 

 legs long, projecting far beyond the carapace; lobes on the basal joints 

 of the posterior pair small and rectangular. Abdomen in the male 

 very much longer, but no modifications of the legs except the regular 

 peg and semen vesicle. No flagella. 



Length, 7.8 mm. ; length of carapace, -i.8 mm. ; breadth of carapace, 

 3.8 mm.; length of abdomen, 'i.'i mm.; breadth, 1.7 mm. 



Color, a yellowish white, mottled along the carapace lobes with 

 brown. Some specimens measure 12 by 6 mm. (See photograph, 

 tig. 80.) 



This species was discovered by Dr. T. W. Harris in 181:1 upon the 

 gills of the ale wife {Chtpea-'^'ernaUs Mitchill).^ 



The single specimen was sent to Dr. A. A. Gould for determination 

 and description; he published a very short and meager description 

 accompanied by a coarse woodcut, from neither of which could any 

 specific characters be determined. The species has rested upon this 

 unsatisfactory basis ever since and has of necessity been more or less 

 doul)tful. It is hoped that the present description and figures will 

 establish it satisfactorily. It occurs in considerable abundance along 

 the Atlantic coast, but has never yet been found on any species of 

 shad, whi(^h mak(\s its name rather inappropriate. 



The Museum collection includes: From the alewife {Poinolohu^ 2:>Heu- 

 duharengas Wilson), Nos. 1310 (by V. N. Edwards), 12680, 11019. 

 From the smelt (sp.), an unnumbered lot, Woods Hole. From 

 vmknown hosts, Nos. 11:10 from Great Egg Harbor; 7739 from Key 

 W^est, and two unnumbered lots, one from Woods Hole and the other 

 from Patchogue, Long Island. This Argulus has also been doubtfully 

 recorded by Mr. J. F. Whitcaves as attached to Gmterosteus hiaciileatus 

 Shaw, in the Gulf of St. Lawrence. 



{alosae = from alosa, the supposed generic name of its host; clupese, 

 would be far more appronriate). 



^ Gould identifies this fish as the European Alosa vulgaris, bu*^ this form does not 

 occur on our coasts, while the alewife is quite common and from it have been obtainet 

 most of the recent specimens. 



