ISOPODS OF NORTH AMERICA. 673 



The segments of the thorax are subequal; the last two have the 

 post-lateral angles produced backward. 



All the segments of the abdomen are distinct. The first two have 

 the lateral parts covered by the seventh thoracic seg- 

 ment. The three following segments have the post- 

 lateral angles produced backward. The terminal 

 abdominal segment is narrow, produced in the middle 

 posteriorly in a long, narrow process, broadly rounded 

 at the apex. The peduncle of the uropoda extends to 

 the end of the terminal abdominal segment. The 

 branches are of nearly equal length. FlG - "is. SCYPHA- 



. , ., , . i CELLA AREXICOLA. 



Color of the specimens, for a long time preserved I SXER LOBE Of 

 in alcohol, dark brown, with the margins of the seg- FIRST MAXILLA. 



,, ,. , , ( DIAGRAMMATIC, i 



ments or a lighter brown. 



Five specimens were collected by Dr. S. D. Judd in the sand on 

 Ram Island, Woods Hole, Massachusetts, and are in the collection of 

 the U. S. National Museum. 



Family XXVIII. LIGYDID^E." 



Body oval. Head without lateral lobes; frontal margin rounded, and 

 not distinctly defined from the epistome. First pair of antennas with 

 the terminal joint not furnished with sensoiy hairs. Second pair of 

 antenna? well developed, with flagellum multi-articulate. Buccal mass 

 prominent. Mandibles with the molar process large and broad, having 

 a finely fluted triturating surface. Inner lobe of the first maxilla? fur- 

 nished at the tip with three plumose processes. Second maxillae also 

 furnished inside with two similar processes. Maxillipeds with the 

 palp composed of five articles; masticatory lobe truncate. 



Opercular branches of pleppods without trachea?. First two pairs 

 of pleopods modified in male; inner branch terminating in a long stylet. 



ANALYTICAL KEY & TO THE GENERA OF THE FAMILY LIGYDID.E. 



. Uropoda with basal article not produced in a process at the inner distal angle; 

 branches equal in length. Last segment of abdomen large, with lateral parts 



well developed Genus Ligyda Rafinesque 



a / . Uropoda with basal article produced in a process at the inner distal angle; 

 branches unequal in length. Last segment of abdomen small, with lateral parts 

 obsolete .. Genus Ligidium Brandt 



123. Genus LIGYDA" Rafinesque. 1814 



Bod}" oval, or oblong oval; abdomen not abruptly narrower than the 

 thorax. Terminal segment broad, with lateral parts well developed. 

 First pair of antenna? with the third or terminal joint rudimentary, 

 nodiform. 



See Sars for characters of family and genus. 



&The genus Euphilosda Packard is not included, as it is probably a synonym of 



Ligidium. 



2858905 43 



