ISOPODS OF NORTH AMEEICA. 161 



half as long as tj>e ramus itself; external ramus narrow, with about 

 eight spines and numerous setas on the posterior and outer margin. 



"This species is close to A. insidaris, from which it differs in its 

 greater hairiness. 



"Two specimens. Station 6079, 20 fathoms, 5 by 2.3 mm." 

 MOORE/' 



28. Genus TRIDENTELLA, new genus. 



First pair of antennae with peduncle composed of three articles. 



First maxillae with the apex of the third article furnished with three 

 spines. Second maxillae indistinctly bilobed at the tip. 



Mandibles becoming narrower from the base to the apex; movable 

 lacinia absent; molar part well developed. 



Clypeus wide and short, in the form of an inverted v, with the 

 post-lateral angles produced almost to the articulation of the mandib- 

 ular palp. 



Labrum small. 



TRIDENTELLA VIRGINIANA (Richardson). 



Cirolana virginiana RICHARDSON, American Naturalist, XXXIV, 1900, p. 216; 

 Proc. U. S. Nat. Mus., XXIII, 1901, pp. 512-513. 



Locality. Chesapeake Bay. 



Depth. 81 fathoms. 



Body not quite twice as long as broad, oval, thickset. Head trans- 

 verse, with indications of four small tubercles, two on the anterior 

 portion, between the eyes, and two on the posterior 

 portion. Eyes large, lateral. First pair of antennae 

 long, nearly as long as the second pair, reaching the 

 posterior margin of the first thoracic segment; flagel- 

 lum twelve-jointed. Second pair of antennae extend 

 to the middle of the third thoracic segment; flagellum FlG 



eigllteen-jointed. TELLA VIRGINIANA. 



First thoracic segment one and a half times longer ctTrera AHD 



than any of the other segments. Following segments R UM. (DIAGRAM- 



, , ,, MATIC.) 



of equal length. 



First abdominal segment almost entirely concealed by last thoracic 

 segment. Four succeeding segments of equal length. Terminal seg- 

 ment very short and narrow, not longer than the four abdominal 

 segments taken together, posteriorly rounded and crenulate. Both 

 branches of the uropoda crenulate. Inner branch broad and equaling 

 in length the terminal segment. Outer branch narrower and a little 

 shorter than inner branch. 



Abdomen minutely granulose. 



Bull. U. S. Fish Comm., XX, Pt. 2, 1902, p. 170. 

 2858905 - 11 



