﻿NO. 7 EMERITA ANALOGA — WEYMOUTH AND RICHARDSON 3 



HABITAT 



The sand crab inhabits a strip of beach in or near the wash of the 

 waves. Here it is distributed from the high-tide limit, for a given 

 tide, to a short distance beyond the point where the waves strike the 

 sand, but the center of abundance is that portion washed by each 

 wave. During a very low tide at Alamitos Bay, the crabs did not 

 follow the wave wash out to its lower limit, but stopped at an inter- 

 mediate point. Further observations at Swanton confirmed this. 



Although occasionally found singly, Emerita is essentially a gre- 

 garious animal. It occurs in large " beds ", which are marked by 

 small V-shaped ripples in the sand. Here, as Leidy has said of the 

 eastern form, they are as thick as currants in plum pudding. If one 

 turns over the sand of one of these beds he will find the sand crab in 

 incredible numbers lying within a few inches of the surface. In 

 these places adults and young of both sexes may be found associated. 

 Generally mature females and males are at once distinguished by the 

 difference in size (see figs, i and 2, pi. 1 ) . For this reason collections 

 often consist of females only, the smaller males being regarded as 

 young. Measurements of the carapace of 2J specimens (length from 

 rostrum to median posterior dorsal margin) of each sex collected at 

 Pacific Grove give the following: average of males (all with enlarged 

 genital papillae) 12.4 mm., range 10.5 to 14.5 mm. ; average of females 

 (all egg-bearing) 21.4 mm., range 17 to 25.5 mm. The males are 

 without pleopods, while the second, third and fourth segments of the 

 abdomen of the females are provided with them. The telson of the 

 adult female is more heavily ciliated along its lateral margin and is 

 somewhat wider than that of the male. The following are measure- 

 ments of two typical specimens : female, length of carapace 20.3 mm., 

 length of telson 13 mm., width of telson 6.9 mm., width 53 per cent of 

 length; male, length of carapace 11 mm., length of telson J.6 mm., 

 width of telson 3.3 mm., width 43 per cent of length. 



The following brief data on the period of egg-bearing in Emerita 

 analoga have been gathered from the material at hand, and, although 

 incomplete, may throw some light on its duration. Of 45 females 

 collected at Swanton on January 5, 191 1, none were carrying eggs, 

 although many young females were present. Out of four females 

 taken at Alamitos Bay on January 4, 191 1, one carried small eggs in 

 which the eye pigment had not appeared. A single adult female from 

 Humboldt Bay, May 28, 191 1, was not egg-bearing. During June, 

 1910, females carrying eggs of all stages from those ready to hatch 

 to those in which the eye pigment had not yet formed were abundant 



