ISOPODS OF NORTH AMERICA. 



4U3 



of the third and fourth soj^meiits are produced on each side into two 

 acute processes — a larger anterior process and a smaHer posterior pro- 

 cess. The epimera of these segments are inconspicuous, as they are 

 small and acute, and lie just underneath the lateral parts about the 

 middle of the segment. In the last three segments the anterior part 

 of the segment is acutely produced, and the acute epimeron occupies 

 the remainder of the lateral margin, the posterior half of the lateral 

 part of the segment not ])eing produced. On each of the first four 

 segments of the thorax is a small tubercle near the posterior margin 

 in the median line. 



The abdomen is composed of one segment only. About one-third 

 the distance from the base to the extremity, on either side the lateral 

 margin is produced in an acute angular process. About two-thirds 

 the distance from the base to the extremity the sides are angulate. 

 From this point the lateral margins converge rapidly to a triangulate 

 extremity, posteriori}' rounded. 



The legs are all more or less alike in structure. 



ERICHSONELLA FLORIDANA Benedict. « 



EriclmmeUa floridana Benedict, in Richakdsox, Proc. U. S. Xat. Mu8., XXIII, 

 1901, p. 543-544. 



LocaliUj. — Key West, Florida, among alga? below low tide. 



The body is long and narrow, broadest at the third and fourth seg- 

 ments. The head is wider than long. A 

 rectangular projection extends forward in 

 front of the eyes. The frontal margin be- 

 tween the projections is arcuate. The eyes 

 are lateral, slightl}' projecting. The antenna^ 

 are geniculate. The three distal segments 

 are approximately the same length. The ter- 

 minal segment or fiagellum is hairy. 



A large tridentate spine occupies the center 

 of the head. The main portion of the spine 

 has a longitudinall}' compressed apex, the lat- 

 eral portions arise at a distance from the base 

 and point divergently forward, falling short 

 of the elevation of the main portion. 



The third and fourth segments of the thorax 

 are the longest and widest; the posterior seg- 

 ments are successividy shorter. The lateral 

 margins of the segments are concave, making 

 the segmental angles acute. The epimera are 

 exposed in th«» concave margins. On the posterior margin of each seg- 

 ment at the median lini* is a single spine pointing backward. On the 



Flfi. 451.— ERICHSONELLA FLORID- 

 ANA (After Benedict). 



"The description that follows is from Doctor Benedict's manuscrijjt. 



