640 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvm. 



LEPEOPHTHEIRUS SALMONIS Krbyer. 

 Plate XXIV. 



Caligus salmonis Kroyer, 1838, p. 13, pi. vi, fig. 7 a-e. 



Caligus vespa Milne-Edwards, 1840, p. 456. 



Caligus slromii Baird, 1847. 



Lepeophtheirus salmonis Baird, 1850, p. 274, pi. xxxn, figs. 8 and 9.— Kroyer, 



1863, p. 137, pi. xvii, fig. 1 a-b.— Rathbun, 1884, p. 487. 

 Lepeophtheirus stromii Baird, 1850, p. 274, pi. xxxn, figs. 8 and 9. — Bassett- 



Smith, 1899, p. 455.— T. Scott, 1900, p. 152, pi. vi, figs. 3 to 8. 



Female. — Carapace orbicular, as wide as long; frontal plates narrow 

 and not well denned; posterior sinuses narrow, shallow, and somewhat 

 inclined away from the median line. Median lobe broad and well 

 rounded, projecting but little be} T ond the lateral lobes, and often raised 

 posteriorly into a fold or wrinkle, which projects over the dorsal sur- 

 face of the free segment and hides it. 



The grooves separating the carapace areas are well denned; the cross- 

 bar of the "H" is strongly curved, so that it makes a continuous half 

 circle with the lower portion of the sides. The free segment is very 

 short and narrow, less than half the width of the genital segment. 

 The latter is nearly as large as the carapace, fully as long but a trifle 

 narrower, with well-rounded lobes projecting posteriorly on either 

 side of the abdomen. The abdomen is four-fifths as long as the genital 

 segment and narrow, with a clearly marked constriction near the 

 posterior end. Such a constriction is usualty good evidence of seg- 

 mentation, but the most rigid examination of the opaque preserved 

 specimens at the author's disposal fails to confirm the segmentation. 

 It is quite possible, however, that living specimens would show it 

 clearly, and for that reason the present species has been included twice 

 in the artificial key herewith presented. The anal laminae are enlarged 

 considerably at the tips and curved in toward each other. 



The egg strings are fully three times as long as the entire body, and 

 at the same time very narrow, which of course emphasizes their elon- 

 gate appearance. 



Of the appendages the second antenna? are stout, with the terminal 

 hook considerably longer than the basal joint; the latter also lacks a 

 spine on its posterior margin. 



The first maxilla? are veiy long and stout, the basal portion swollen 

 to about twice the diameter of the terminal curved part. 



The second maxilla? are of the usual size and shape. The first max- 

 illipeds are stouter than usual, the terminal joint more than twice the 

 length of the basal. The shorter terminal claw is about three-fifths 

 the length of the longer one, and is dentate along its outer margin. 

 In the second maxillipeds the terminal claw is only about half as long 

 as the basal joint, and in all the specimens examined it lacked an acces- 

 sory spine on the inner margin. The furca is proportionally small, 



