﻿COPEPODS FROM LAKE ERH HAI, CHINA — ^HSIAO 



197 



rami of first three pairs of legs and all of the fourth visible from the 

 dorsal side. Compound eye of medium size, median eye small, dis- 

 tance from anterior end of median eye to tip of carapace 23.34 ±0.50 

 percent of total length of animal. Anterior end of dorsal ridge 

 forked. Abdomen nearly elliptical, with two sides parallel for a 

 greater part of their length, abdomen 56.62 ±2.05 percent of total 

 length, anterior end contracted into a short neck where it joins the 

 thorax, each side of this necklike portion carrying a triangular process 

 (fig. 25, a) — a structure not described by earlier authors. Anal sinus 

 38.44 ±0.81 percent of abdomen length, each caudal ramus in two 

 sections, a broader basal portion, arising from the anterior end of the 



2 30 40 60 80 



B 



T()TA_ LENGTH 



Ui 



4 5 6 7 8 9 



Figure 30. — A, Abdomen length plotted against total length of Argulus japonicus, dots 

 based on data from animals larger than 3.5 mm. and crosses based on those of smaller 

 ones; B, carapace length plotted against total length of argulids smaller than 3.5 mm. 

 long, scales in ocular division of microscope. 



abdominal sinus, and a slenderer distal portion bearing seta on its 

 caudal end (fig. 25, d) — this has not been described thus before. 

 Antenna, maxilliped, and swimming legs as given by Thiele (1904), 

 Tokioka (1936), and Meehean (1940) and as shown in figure 25, h-e. 

 Sucking disk with 38-50 supporting ribs, average 44-45, two sucking 

 disks of the same animal with different number of ribs, each rib con- 

 sisting of one long basal and five short distal segments, decreasing in 

 size distally. Width of animal 64.92 ±0.234 percent of total length. 

 Adult male: The males show comparatively less variation than 

 the females in the characters measured. Carapace smaller than in the 

 female, being 63.45 ±.048 percent of total length; compared with that 



