COPEPOD GENUS HEMICYCLOPS — GOODING 165 



sixth legs will most easily differentiate adult males from females. 

 Dissection should not be necessary in following the key but use of a 

 compound microscope and generally some preliminary clearing 

 treatment (discussed on p. 162) will be essential. 



1. Setulose exopod spines only on first leg; terminal segment of antenna very 



little longer than wide thysanotus (p. 1G5) 



Setulose spines on exopods of all 4 swimming legs; last antennal segment more 

 than 2 times as long as wide 2 



2. Antenna with 2 large, elliptical patches of fine spinules on inner side of second 



and third segments; distal podomere of fifth legs without spinules on sides. 



arenicolae (p. 188) 



Antenna without spinules as above; distal podomere of fifth legs with some 



spinules on sides 3 



3. Caudal rami more than 4 times as long as wide; body more than 2.7 mm. in 



length elongatus (p. 181) 



Caudal rami less than 3 times as long as wide; body less than 2.5 mm. in 

 length 4 



4. Innermost spine on distal segment of fifth legs about equal in length to adjacent 



seta; ventral spine on maxilliped with 2 denticles on anteroventral sur- 

 face adhaerens (p. 176) 



Innermost spine on distal segment of fifth legs shorter than adjacent seta; 

 ventral spine on maxilliped With 3-5 denticles on anteroventral sur- 

 face subadhacrens (p. 181) 



Hemicyclops thysanotus Wilson 



Figures 1; 2; 3,a-c 



Hemicyclops thysanotus Wilson, 1035, pp. 783-785, pi. 28, figs. 41-52. — Light and 



Hartman, 1937, pp. 179-180, pi. 12, figs. 3-4.— Nicholls, 1944, pp. 44, 40 — 



Sewell, 1949, pp. 67, 69. 

 Hemicyclops callianassae Wilson, 1935, pp. 782-783, pi. 27, figs. 25-35. — Light and 



Hartman, 1937, pp. 179, 180.— Nicholls, 1944, pp. 45, 49— Sewell, 1949, p. 67. 

 Hemicyclops pitgeltensis Light and Hartman, 1937, pp. 170, 180, 181-182, 182, 



t.-figs. 12-20, pi. 12, figs. 5-6.— Nicholls, 1944, pp. 45, 49.— Sewell, 1949, pp. 



67, 68, 69.— Gooding, 1958, p. 699 (part). 



Types: "A single female bearing ovisacs and a male . . . from the 

 outside surface of the eolid, Hermissienda [sic] crassicornis, in Elkhorn 

 Slough, Monterey Bay" (Wilson, 1935), USNM 64063, here considered 

 syntypes. 



The designated types for callianassae were "a single female with 

 attached male" (Wilson, 1935), USNM 60432. Of these only the 

 male syntype appears to be still in existence (letter from Dr. T. E. 

 Bowman, February 25, 1958). II. pugettensis was stated by Light 

 and Hartman (1937, p. 182) to be based on a single specimen, but 

 the catalog number that they quote (USNM 71678) comprises a 

 (syntypic) series including females and males. There is no record 

 of a holotype in the U.S. National Museum. 



Material examined: From Ilermissenda crassicornis: Cl (see 

 p. 160) : 1 female, 1 male, syntypes of thysanotus. 5 females, 3 males, 



