60 RATHBUN 



H. MaxilHped with exopod pusiola. 



H'. Maxilliped without exopod. 



J. Antennal scale about same length as, or shorter 



than, telson brevirostris. 



]'. Antennal scale longer than telson . . palpator. 

 F'. Rostrum reaching second segment of antennular pe- 

 duncle. 



G. Rostrum straight herdmani. 



G'. Rostrum arched over the eye. 



H. Fourth segment of abdomen with lateral spinule. 

 Maxillipeds reaching, or nearly reaching, end of 



acicle cristata. 



H'. Fourth segment of abdomen unarmed. Maxillipeds 

 reaching only to distal third of acicle . stoneyi. 



SPECIES OF SPIRONTOCARIS, ARRANGED ACCORDING TO THEIR 

 EXOPODS AND EPIPODS. 



A. One or more supraorbital spines present. 

 B. Third maxilliped with exopod and epipod. 



C. First thoracic foot with epipod sua. 



C First and second thoracic feet with epipods . bispinosa, snyderi. 

 C", First, second, and third thoracic feet with epipods 



prionota, lamelluornis, spina, arcuaia, murdochi, 

 iruncata? , liljeborgii, phippsii, ochotensis, dalli. 

 B'. Third maxilliped without exopod but with epipod. 



C. First thoracic foot with epipod vicina. 



C. First and second thoracic feet with epipods polaris, unalaskensis. 

 C". First, second, and third thoracic feet with epipods 



grcenlandica, washingtoniana. 



B". Exopods and epipods unknown qffinis, 



A'. No supraorbital spine or spines. 



B. Third maxilliped with exopod and epipod. 



C. Thoracic feet without epipods barbata, biunguis, macrophthalma. 

 C. First thoracic foot with epipod 



fabricii (usually), suckleyi (usually). 

 C". First and second thoracic feet with epipods 



/abricii (sometimes), gawiardii bel- 

 cheri, iownsefidi, suckleyi (sometimes). 

 C". First, second, and third thoracic feet with epipods 



pusiola, herdffiani, stoneyi, avina, macilenta, 

 B'. Third maxilliped without exopod but with epipod. 

 C. Thoracic feet without epipods 



decora, tridens, stylus, maxillipes, 

 brachydactyla, camtschatica, kincaidi. 

 C. First thoracic foot with epipod .... moseri, sitchensis. 

 C", First and second thoracic feet with epipods 



^exa, picta, paludicola. 

 C". First, second, and third thoracic feet with epipods 



carinata, palpatory brevirostris, taylori, cristata. 



