UNIVERSITY OF CALIFORNIA PUBLICATIONS 



ZOOLOGY 



Vol. 16, No. 23, pp. 431-438, 1 figure in text April 16, 1917 



NOTES ON THE NATURAL HISTORY AND 

 BEHAVIOR OF EMERITA ANALOGA 



(STIMPSON) 



BY 



HAROLD TUPPBR MEAD 

 (Contribution from the Scripps Institution for Biological Research, La Jolla, Cal 



Along sandy beaches in the vicinity of San Diego are countless 

 numbers of the burrowing crustacean, Emcrita analoga (Stimpson) 

 commonly called the sand-crab. They are roughly oval creatures 

 having an elongate, transversely rounded carapace which, in adult 

 females, has an average length of about 22.4 millimeters and an 

 average width of about 17 millimeters, computed from measurements 

 of twenty-three individuals. Adult males have a carapace length of 

 from 12 to 14 millimeters (Barnliart). The abdomen and telson re- 

 semble somewhat those struetui'es in the true crabs. The first pair 

 of pereopods are simple, flattened and extended forward a little in 

 advance of the head. The other pereopods are less conspicuous, being 

 shorter and not protruded so far from underneath the body. The 

 eyes are mounted on comparatively long, slender stalks. These crabs 

 always move backwards, whether swimming, crawling or burrowing. 

 Swimming is accomplished almost entirely by the backward beating 

 of the uropods above the posterior margin of the carapace, thereby 

 drawing the animal through the water. Burrowing is accomplished 

 by the combined action of the uropods and pereopods, the latter being 

 the more serviceable. Animals from which the uropods were clipped 

 could not swim, while apparently making frantic efforts, but they could 

 burrow, although more slowly than normal animals. When the pereo- 

 pods were clipped and the uropods left, the animals could swim like 



