S58 Puget Sound Marine Sta. Pub. Vol. 1, No. 30 



Family GRAPSIDAE 

 Genus Hemigrapsus 



• KEY TO SPECIES 



A. Legs smooth and free from hairs; hands spotted. 1. //. nudus 



AA. Legs smooth but hairy; hands not spotted. 2. H. oregonensis 



1. Hemigrapsus nudus (Dana) Rathbun. purple shore crab 



(figs. 1, 2, 3, 9) 



Pseudograpsus nudus Dana; Heterograpsus nudus Stimpson; Hetero- 

 grapsiis sanguineus Kingsley; Brachynotus nudus Hohiies. 



Rostrum none. Antennae short, inconspicuous. Carapace roughly 

 rectangular, anterior part convex and undulated ; posterior margin straight 

 except at each end where it is concave to make a place for the attachment 

 of the last pair of walking legs ; front of 2 lobes with comparatively 

 broad and shallow emargination ; the 2 prominences behind the front about 

 evenly rounded ; 3 teeth on the anterior lateral margin counting the post 

 orbital one as the first, first 2 markedly convex, the last very much smaller 

 and less prominent than the others ; surface of the carapace smooth, punc- 

 tate, curved line of white pits from the H-shaped depression in the center 

 to the last antero-lateral tooth. The line of teeth or granulations on the 

 pterygostomian region run practically parallel to the antero-lateral mar- 

 gin and are larger and farther apart on the posterior end of the line, 

 .^laxillipeds punctate with round edge on inner margin of ischium and 

 raerus. Chelipeds large, powerful; merus trigonous with rounded projec- 

 tions at distal end; carpus with prominent projection on inner surface; 

 hands smooth, inflated ; fingers toothed ; large patch of long soft hairs on 

 the inner palms of the chelipeds of the males. Predominating color red- 

 dish purple flecked with dirty white; hands always spotted. 



Often great variation in color is noted ; some are green and black 

 without any indication of purple, while others are reddish brown ; often 

 there are large irregular spots of dirty white on the carapace and in 4 

 instances the whole carapace save for a tiny spot on the posterior margin, 

 was dirty white. This great variation in color and markings was noted 

 only among the smaller specimens, yet many of these were sexually mature 

 and were carrying eggs. One of those bearings eggs was 15 mm. wide 

 and 1-i mm. long; the carapace of the largest found was 37 mm. long, il 

 mm. wide. They are abundant everywhere along the shore below the high 

 tide line. Some hide under rocks and stones and others run about under 

 the algae out from the shore. On several occasions they were found on the 

 piles under the Friday Harbor docks (4). 



