FISHERY BULLETIN: VOL. 78, NO. 1 



species show characteristics intermediate be- 

 tween groups. 



Several extensive keys exist. Benedict's (1902) 

 key describes all specimens in the U.S. National 

 Museum collection at that time. Chace (1942) 

 wrote a key to the western Atlantic species, which 

 has been updated by Pequegnat and Pequegnat 

 (1970, 1971). Other extensive keys were con- 

 structed by Milne-Edwards and Bouvier (1894) 

 and Alcock (1901). 



Characteristics of 

 Taxonomic Importance for Species 



Although the antennular peduncle, antennal 

 peduncle, and merus of the third maxilliped are 

 usually drawn for new species, these characters 

 are rarely used to identify species. 



Carapace. Presence, absence, and number of 

 spines on the anterior, lateral, and posterior mar- 

 gins and on the dorsal surface of the carapace. 



Presence of the antennal spine variable among 

 specimens of the same species. The basic type of 

 ornamentation (ridges, tubercles, crenulations, 

 spines, setae) on the dorsal surface. Slight differ- 

 ences in ornamentation, size, and spacing found on 

 specimens from different geographic locations are 

 considered varietal differences. 



Rostrum. The general shape: triangular or 

 rounded. Lateral margins armed with spines or 

 unarmed. 



Eyespines. Presence or absence; length in rela- 

 tion to cornea; sharp or blunt. 



Chelipeds. Length compared with carapace 

 length; ornamentation, especially spines on seg- 

 ments. 



Walking legs. Not as important as chelipeds. 

 General ornamentation. 



Epipodites on chelipeds and legs. Presence or 

 absence. 



Abdomen. Presence or absence of spines on dor- 

 sal surface. 



Key to Species of Munidopsis off Oregon and Washington 



la. No epipods on chelipeds 2 



lb. Epipods present on chelipeds 5 



2a. Eyespines absent; one large spine on second, third, and fourth abdominal segments; 



frontal and lateral margin of carapace forms a right angle quadrata 



2b. Eyespines present; abdomen unarmed; spine or tooth present at anterolateral corner of 



carapace 3 



3a. Wide, triangular rostrum; posterior margin of carapace unarmed aries 



3b. Narrow rostrum with or without lateral spines; posterior margin of carapace armed with 1 



to 10 spines 4 



4a. Rostrum with 2-6 lateral spines, posterior margin of carapace armed with 3-10 (usually 



4-6) spines; chela with 2 inner spines bairdii 



4b. Rostrum with no lateral spines; posterior margin of carapace armed with one spine; chela 



without two inner spines sp. 



5a. Eyestalks extend beyond eye as definite, sharp spines 6 



5b. Eyestalks extend beyond eye as blunt processes 11 



6a. Two eyespines present, a longer inner spine and a short outer spine ciliata 



6b. Only inner eyespine present 7 



7a. Rostrum wide, not triangular, with dorsal carina, rounded at end yaquinensis 



7b. Rostrum triangular, with dorsal carina and pointed at end 8 



8a. Carapace and legs covered densely with setae; lateral margins of carapace 



without spines cascadia 



8b. Carapace and legs not covered densely with setae; spines on lateral margins of carapace 9 



16 



