256 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



mm. The post-lateral angles are rounded, and the posterior margin 

 is slightly excavate in the middle. The uropoda are as long as the 



terminal abdominal segment. 

 The outer branch is slightly 

 shorter than the inner branch. 

 Both are equal in width, 

 and narrow, with extremities 

 rounded. 



The legs are all prehensile, 

 with short, stout, curved dac- 

 tyli. There is a high carina 

 on the basis of the last four 

 pairs, the carina increasing 

 gradually from the fourth to 

 the seventh pair, where it is 

 extremely high." 



42. Genus LIVONECA 

 Leach. 



Body suboval, more or less 

 twisted. 



Head most always deeply 

 immersed. First pair of an- 

 tennae widety separated at the 

 base, rather compressed. 



Anterior margin of the first 

 thoracic segment widely sin- 



uated in the middle, more or less sinuated or incised at the antero- 

 lateral angles. 



Abdomen very little immersed, continuous with thorax, not nar- 

 rower than thorax. 



FIG. 264. CYMOTHOA CESTRUM. a, MAXILLIPED. 

 6, SEVENTH LEG. x 4}. c, FIRST MAXILLA. 

 d, SECOND MAXILLA, x 15$. e, MANDIBLE. 



/, PALP OF MANDIBLE. X 15}. 



x 15}. 

 x 15}. 

 X 15}. 



ANALYTICAL KEY TO THE SPECIES OF THE GENl'S I.IVONECA. 



a. Abdomen somewhat immersed in thorax, the sides of the first segment being 



almost entirely covered by the seventh thoracic segment. 

 b. Head quadrate, but little broader at the base than at the anterior end. 



Livoneca panamensis Scrmrdte and Meinert 



b' '. Head triangular, nearly twice as broad at the base as at the anterior extremity, 

 c. Head roundly truncate in form. Terminal segment of abdomen nearly twice 



as broad as long Livoneca vulgaris Stimpson 



c f . Head narrowly rounded in front. Terminal segment of abdomen about as 



long as broad Livoneca calif ornica Schioedte and Meinert 



a'. Abdomen not immersed in thorax, the sides of the first segment free. 



a For complete description of this form, the male and female and the young of 

 the first and second stages, see Schicedte and Meinert, Nat. Tidsskr. (3), XIV, 

 1883-84, pp. 271-278 



