NO. 2063. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 



573 



The size of the process is somewhat proportional to the size of the 

 male; in the genus Clavella both the male and the process are very 

 small, while in Brachiella the males are large and the process is 

 increased proportionally. 



In the cephalothorax the general relations and the varying struc- 

 ture of the head, neck, arms, and trunk furnish very useful generic 

 characters. We may distinguish first genera in which the head 

 and neck are long and slender and flexed dorsally at an angle with the 

 trunk. The second maxillae may be in the same line with this elong- 

 ated cephalothorax and of about the same length, the two standing 

 across the anterior end of the trunk 

 like the top of the letter T (Brachiella, 

 Thomsonella, Brianella) . 



Or the second maxillae may be 

 much shorter than the cephalothorax 

 and inclined at a different angle (Cla- 

 vellodes, Clavellopsis, NaohrancMa) . 

 Sometimes the cephalothorax is bent 

 back so far that it rests agamst the 

 dorsal surface of the trunk and the 

 creature looks as if it were folded and 

 hung from the bend of the fold {Cla- 

 vella). And in one genus (new) there 

 has been a fusion after such a bend- 

 ing, and as a result the cephalothorax 

 is attached to the center of the dorsal 

 surface of the trunk and stands out at 

 right angles to the axis of the latter, 

 while the second maxillae are attached 

 to the anterior end of the trunk some 

 distance from the base of the cephalo- 

 thorax (Clavellisa). 



In a second group we fmd genera m which the head and neck are 

 shorter and stouter, and they either stand in line with the axis of the 

 trunk or are curved over (not flexed at an angle) ventrally . The second 

 maxiUae may also be short and stout and stand out at right angles to 

 the trunk axis, and they as well as the posterior margin of the trunk 

 may be hung with fimbriate processes (Thysanote, Tliysanotella) . Or 

 they may be perfectly smooth w^hile the posterior margin of the trunk 

 is furnished with cylindrical processes {Brachiella, Epihrachiella) . 



Again the second maxillae may be long and slender and inclined at 

 an acute angle to the trunk axis, either forward or backward. 



They may be entirely separate, each ending in a clasping process 

 (Oharopinus) , or they may be joined by an ordinary bulla. In this 



Fig. 1.— Section of Clavella xjncinata 

 SHOWING a, anus; go, genital opening; 

 gp, genital process; sr, sperm recep- 

 tacle; St, SPERM TUBE; i, INTESTINE. 



