Table l. — Morphological characteristics for distinguishing 

 between Stage I and II zoeae of the subfamily Oregoniinae. 



gin of the teisonic furcations. In addition, the 

 Stage II zoeae bear supraorbital spines which are 

 lacking in the Stage I zoeae. 



Hart (1960) reared and described the larvae of 

 H. lyratus and O. gracilis from ovigerous females 

 collected in British Columbia waters. Based on 

 Hart's brief description, Stage II zoeae H. lyratus 

 and O. gracilis are similar morphologically to 

 Stage II zoeae of C. bairdi, but markedly smaller. 

 Dorsal-rostral length of Stage II H. lyratus andO. 

 gracilis averages 4.0 mm and 4.5 mm, respec- 

 tively, compared with 6.5 mm for Stage II zoeae of 

 C bairdi. 



Kurata (1963) described larvae collected off 

 Hokkaido that he provisionally identified as H. 

 coarctatus alutaceus. They can be distinguished 

 from Stage II zoeae of C. bairdi by their smaller 

 size (dorsal-rostral length averages 4.4 mm) and 

 the lack of a distinct protuberance posterior to the 

 dorsal spine. 



Stephensen (1935) described zoeae from the col- 

 lection of the Zoological Museum of Copenhagen 

 previously identified by C.N. Rudolph and sub- 

 sequently believed by Stephensen to be zoeae of 

 C opilio. Because of the numerous (14) natatory 

 setae on the exopodites of the maxillipeds, 

 Stephensen's zoeae are obviously not zoeae of the 

 genus Chionoecetes nor even of the Oxyrhyncha. 

 Stephensen's zoeae undoubtably belong to the 

 Brachyrhyncha and likely the families Atelecyc- 

 lidae or Cancridae. 



Kurata (1963) described Stage I zoeae of C. 

 opilio elongatus (=C. opilio^) reared in the 

 laboratory from known parentage and the re- 

 maining larval stages from plankton of the Hok- 



iRathbun ( 1924) designated C. opilio in the Sea of Japan as C. 

 opilio elongatus based on the length/width relation of the second 

 merus. According to Tohshi Kon, Fukui Prefecture Fishery Ex- 

 perimental Station, Tsuroga-shi.Fukui-Prefecture, Japan (pers. 

 commun. November 1978), Kamita's (1941) findings invalidate 

 Rathbun's subspecific designation. 



kaido area. Motoh (1973) described the zoeal and 

 megalopal stages of C. opilio reared in the 

 laboratory from an ovigerous female caught in 

 the Sea of Japan. I confirmed Kurata's and 

 Motoh's brief descriptions of Stage I and II zoeae 

 by comparing their descriptions with specimens 

 from the Sea of Japan sent to me by Tohshi Kon 

 (see footnote 1). For both stages, zoeae of C bairdi 

 are morphologically identical with zoeae of C. 

 opilio from Hokkaido and the Sea of Japan, except 

 for length of the curved lateral processes on the 

 third abdominal somite. In Stage I and II zoeae of 

 C. opilio from Hokkaido and the Sea of Japan, 

 the curved lateral processes reach the posterior 

 margin of the third abdominal somite, but, in 

 Stage I and II zoeae of C. bairdi, they are mark- 

 edly shorter (Figure 2A, L). 



Apparently larvae of C. japonicus are known; 

 but, except for a brief comparison of their mor- 

 phology with larvae of C. opilio by Yamauro 

 (1968), I am unaware of their description in the 

 literature. Based on Yamauro's comparison. Stage 

 I and II zoeae of C. japonicus are distinguished 

 from Stage I and II zoeae of C. bairdi by length of 

 the posterior lateral spines on the third, fourth, 

 and fifth abdominal somites. In C japonicus 

 zoeae the posterior lateral spines barely reach the 

 posterior margin of the somite, but in C. bairdi 

 zoeae they extend beyond the margin. 



The following key is provided for distinguish- 

 ing Stage II zoeae of C. bairdi from Stage II zoeae 

 of C. opilio, C. japonicus, and the genera Hyas 

 and Oregonia. In the key, length of the lateral 

 processes on the third abdominal somite of C. 

 opilio zoeae is based on specimens from the west- 

 ern Pacific Ocean. Stage II zoeae of C. opilio from 

 the eastern Pacific Ocean have not been iden- 

 tified, and it is not known whether they can be 

 distinguished from Stage II zoeae of C. bairdi by 

 length of their lateral processes. 



Key for Distinguishing Stage II Zoeae C. bairdi 



la. Dorsal-rostral length 4.0-4.6 mm 



Hyas, Oregonia 



lb. Dorsal-rostral length 6.0-6.9 mm 2 



2a. Lateral processes on third abdominal 

 somite reach posterior margin of 

 somite C. opilio 



2b. Lateral processes on third abdominal 

 somite do not reach posterior margin 

 of somite 3 



3a. Posterior lateral spines on abdominal 



181 



