but the water reaches them through an orifice 

 extending around the hinder border of the carapace 

 and is kept circulating and replenished by the 

 rapid vibration of a pair of scoops, or scaphog- 

 nathites, at the base of the second pair of jaws. 

 The bailing action of this scoop draws the water 

 over the gills and sends it forth from the mouth 

 region in a constant stream. Nor was the respira- 

 tory apparatus of my spider-crab an exception to 

 this. However, in examining the molt, I was struck 

 with the structure of the antennae — their unusual 

 length and the fact that they had an arrangement 

 of short bristles which, when the feelers were 

 brought together, would form a tube, made me 

 think that here might exist some relation to its 

 manner of breathing. 



Such was the fact. But it did not in itself solve 

 the problem. As a rule, the head region in most 

 crabs contains only the exhalant orifices, the 

 water first entering near the attachment of the 

 walking legs. Then, too, the spider-crab, unlike 

 other mud-dwelling crustaceans which carry on 

 their legs a fringe of hairs to filter out the silt, is 

 devoid of any exterior straining device. So, unless 



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