ORAL APPENDAGES OF MARINE ISOPODA. 85 



the same width as the epipodite and shorter than the palp. The four-jointed 

 palp has the first joint small, the second joint longer than the third though 

 not so expanded laterally, and the fourth joint considerably larger and oval 

 in shape. The inner distal lobe is elongated, extending almost to the end of 

 the third joint of the palp ; terminally it has some strongly developed plain 

 spines and a number of setose ones. The epipodite extends just beyond the 

 anterior margin of the second joint of the palp. 



Erichsonella, Benedict. 



16. Erichsonella attenuata (Harger). (PI. 8. fig. 34 ; PL 9. fig. 35.) 



Erichsonia attenuata, Harger with Verrill, Rpt. U.S. Conims. F. & F. 1873, pt. I. p. 570, 

 pi. 6. fig. 27 ; Harger, ibid. 1880, pt. vi. p. 356, pis. 6, 7. figs. 36, 37. 



Erichsonella attenuata, Richardson, Bull. No. 54, U.S. Nat. Mus. 1905, p. 400, figs. 447, 

 448. 



The First Maxilla (PL 8. fig. 34). — The outer lobe terminates in ten spines, 

 the middle ones being the largest, two or three of the innermost are faintly 

 denticulate. The inner lobe has the anterior margin sloping inwardly and 

 has sometimes four and sometimes three setose spines and a setule on the 

 outer margin ; the inner margin is setose. 



The Maxillipede (PL 9. fig. 35). — Miss Richardson's figure shows three 

 divisions of the coxopodite, but I have failed to find more than two. The 

 basipodite is rather short and a little narrower than the epipodite. The palp 

 has four wide joints, the first being small and the second and third cup-shaped 

 and gradually enlarging, their inner margins are widely expanded, the fourth 

 joint (the largest) is oval in shape. The setae are small and few in number. 

 The inner distal lobe extends almost as far as the anterior margin of the ihird 

 joint of the palp. The epipodite is almost truncate at its posterior margin 

 and narrows a little anteriorly and extends just beyond the middle of the 

 third joint of the palp. 



Synoptic Key to the Species of the Gams Synidotea. 



A. Terminal segment of metasome emarginate or notched. 

 a. Lateral cephalic lobes well developed. 

 b. Frontal spines overhanging frontal lobe. 



c. Outline of metasome triangular \ S. hiriipes (Milne-Edw.). 



I <S'. pallida, Benedict. 

 b'. Frontal spines absent. 



c'. Outline of metasome subparallel >S'. nebulosa, Benedict. 



c'. Outline of metasome arcuate . S. anyulata, Benedict. 



c'". Outline of mesosome subtriangular. 



d. Outline of metasome subparallel & marmorata (Packard). 



a'. Outline of mesosome strongly arcuate <S\ bieuspida (Owen). 



