NO. 2063. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 649 



THOMSONELLA, new genus. 



Generic characters of female. — Cephalo thorax half the length of the 

 second maxiUae, the two in the same line and at right angles to the 

 trunk axis; trunk pear-shaped and a little longer than the cephalo- 

 thorax, indistinctly divided into four segments; two slender poste- 

 rior processes dorsal to the egg strings; a rudimentary abdomen but 

 no anal laminae; maxilhpeds at the center of the space between the 

 second maxillae and the mouth tube, smaU and rudimentary; second 

 maxillae long and free to their tips where they are joined to an ordi- 

 nary bulla. First antennae two-jointed, the basal joint the longer; 

 second antennae biramose, exopod much larger than the endopod, 

 both unsegmented; fii-st maxillae tipped with three setae, and bear- 

 ing a palp -vvith two terminal setae. 



Male . — Unlaio wn. 



Type. — Tliomsonella jMrJceri {Bracliiella parlceri Thomson). 



{ThomsoneUa, to Prof. George ^C. Thomson, of the University of 

 New Zealand, who first described the type-species.) 



RemarTcs. — This new genus is estabhshed for the species described 

 under the name Brachiella parlceri by Prof. Thomson in his "Par- 

 asitic Copepods of New Zealand,"^ and afterward (1909) by Miss 

 May E. Bainbridge,^ who placed a question mark in front of the 

 genus name. That it can not belong to the genus BracUelU is at 

 once evident from the position and degeneration of the maxilhpeds, 

 as well as from the structure of the other mouth parts. It does not 

 possess a single character assigned to the genus Brachiella except the 

 large size and the separation of the second maxillae. It shows a 

 close relationship to the new genus Brianella in the position and 

 structure of the maxilhpeds and in the general make-up of the entire 

 body. But it differs fi"om that genus in the structure of the fii-st 

 antennae, the mouth tube, and the second maxillae, and may be 

 recognized simply by the presence of the buUa instead of the branched 

 horns. It serves to place the now subfamily on a more secure founda- 

 tion, and in the possession of a bulla it shows that the same variety 

 exists in the new subfamily as in the older ones. 



CJ1.AVELIL.IN-^K, new subfamily. 



Subfamily characters of female. — Cephalothorax much longer than 

 the second maxillae and often bent backward until it rests against the 

 dorsal surface of the trunk; usually narrow and wormhke; trunk 

 flattened dorso-ventrally, with pau-ed posterior processes, sometimes 

 as many as six or eight, aad often with an unpaired genital process; 

 usually no abdomen and no anal laminae; maxillipeds close to the 



1 Trans. New Zealand Institute, vol. 22, p. 374. 



2 Trans. Linnaean Society, ser. 2, Zool., vol., 11, p. 62. 



