18 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



branch not being di.stinctl}' defined from the peduncle, branches 

 unequal, inner one larger and biarticulate, outer one composed of one 

 or two articles. Incubatory pouch normal. Mandibles small and 

 feeble in structure, cutting part narrow, molar expansion forming a 

 thin acuminate lappet armed at the tip with a few small denticles. 



ANALYTICAI, KEY TO THE SPECIES OP THE GENUS LEPTOGNATHIA. 



a. In female the inner Ijraneh of the uropoda is twice as long as the outer. The 

 second or first free segment of the thorax is about two-thirds as long as the 

 third, which in turn is about equal to the fourth and fifth. Sixth and seventh 

 segments progressively somewhat shorter. Propodus of first pair of legs less 

 robust than carjius Leptognathia acca ( Harger ) 



a'. In female the inner branch of the uropoda is more than three times as long as the 

 outer. The second or first free segment of the thorax is about the same size as 

 the last one, both being shorter than the others. Propodus of the first pair of 

 legs scarcely smaller than the carpus Leptognathia longiremis (Lilljeborg) 



LEPTOGNATHIA CiECA (Harger). 



Paratanais cseca Harger, Am. Jour. Sci. (3), XV, 1878, p. 378. 



Leptnchelia cxca B^ARGmi, Proc. U. S. Nat. Mus., II, 1879, p. 164; Keport U. S. 



Commissioner of Fish and Fisheries, 1880, Pt. 6, pp. 427, 428; pi. xiii, 



fig. 91. 

 Leptognathia aeca Sars, Archiv for Math, ognaturvid., 1882, p. 45. — Norman and 



Stebbing, Trans. Zool. Soc. Lond., XII, 1886, Pt. 4, p. 110. — Richardson, 



American Naturalist, XXXIV, 1900, p. 211; Proc. U. S. Nat. Mus., XXIII, 



1901, p. 502. 



Localities. — Massachusetts Ba}', off Salem; Provincetown, Massa- 

 chusetts. 



Surface to 48 fathoms in soft nuid. 



"This species is at once recognized among 

 our Tanaids by the absence of eyes. The en- 

 larged chelate claws joined to the united head and 

 first thoracic segment, and the six-jointed pleon 

 serve to distinguish it as belonging to the present 

 genus. 



•'Body slender, elongated, and rather loosely 

 articulated; head narrow in front, not broader 

 than the bases of the antennuhe; ej^es wanting; 

 antcnnulie distinctly four-jointtMl in the type speci- 

 men, first segment forming less than half the 

 length of the organ, second segment longer than 

 the third, last segment about as long as the sec- 

 ond, slender, tapering, and tipped with seta^; an- 

 tenna^ attaining the tip of the third anteniudar segment. The first 

 pair of legs are robust, but less so than in the preceding species {Lep- 

 tochelia fluiii)\ they extend forward in the natural ])ositi()n about to 

 the tips of the antenna^; they have the basal segment sulxiuadrate, the 

 hand or propodus less robust than the carpus, w ith a serrated digital 

 process; dactylus short. 



Depth, 



Fig. 21. — Leptognathia 

 c^cA (After Hargee). 

 o, First antenna, x 60. 

 6, Leg op first pair. 

 X 50. c, Uropod. x~50. 



