BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



minal segment is 10 mm. wide at the base. The sides converge from 

 the base to a point about the middle, where the segment is 8 mm. in 

 width. From the middle to the extremity the abdomen is of equal 

 width. The abdomen terminates in an extremity, which is acutely 

 pointed in the middle of the posterior margin and has the post-lateral 

 angles pronounced and rounded, but not produced. 

 All the legs are similar in structure. 



61. Genus SYNIDOTEA Harger. 



Flagellum of second antenna multi-articulate. Palp of maxillipeds 

 composed of three articles. Epimera of all the thoracic segments per- 

 fectly and firmly united with the segments. In the last three segments 

 there is sometimes a faint depression marking the place of coalescence. 

 The abdomen is composed of a single segment, with a suture line on 

 either side at the base indicating another partly coalesced segment. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS SYNIDOTEA. 



a. Terminal segment of body emarginate or notched at the extremity. 

 l>. Two spines or tubercles overhanging the frontal notch. 



c. Antero-lateral processes produced horn-like Synidotea ritteri Richardson 



</. Antero-lateral processes not produced horn-like. 



d. Spines united near the base Synidotea pallida Benedict 



d' '. Spines free at base Synidotea erosa Benedict 



b' '. No spines or tubercles overhanging the frontal notch, 

 c. With a low ridge arising between the eyes and interrupted on the median line. 



d. Outlines of abdomen subparallel Synidotea nebulosa Benedict 



d / . Outlines of abdomen strongly arcuate Synidotea angulata Benedict 



c' . Without a ridge between the eyes. 

 . d. Outline of abdomen subtriangular. 



e. Front not excavated Synidotea consolidata ( Stimpson) 



ef. Front excavated. 



/. Outlines of thorax subparallel Synidotea marmorata (Packard) 



/'. Outlines of thorax strongly arcuate Synidotea bicuspida (Owen) 



d'. Outlines of abdomen rounded. 



e. Length of abdomen equal to width at base Synidotea laticauda Benedict 



e f . Length of abdomen equal to one and one-half times the width at base. 



Synidotea harfordi Benedict 

 a'. Abdomen pointed. 



b. Undulations of the body not tubercular or spiny. 



c. Tubercle in front of the eyes not margined Synidotea nodulosa ( Kr0yer) 



cf . Tubercle on the frontal margin and forming a part of it. 



Synidotea Isevis Benedict 



b'. Undulations of the body tubercular and spiny, 

 c. Four spines on the front of the head; body spinous. 



Synidotea muricata (Harford) 

 (/. A wedge-shaped tubercle behind the frontal notch; body tubercular. 



Synidotea picta Benedict 



