174 University of California Publications in Zoology [Vol. 23 



Dimensions. — Length of carapace 29 mm., width 23 mm., length of telson 

 19 mm., width of telson 9.5 mm., length of abdomen when extended 37 mm. The 

 ratio of the length of the carapace to its width is quite variable (Holmes). The 

 length of the carapace of the Biological Survey specimens ranged from 10 to 25 

 mm., averaging about 17 mm. 



Color. — A bluish or cinereous color above and yellowish white below; the 

 fringing hairs are mostly black (Stimpson). 



Type Locality. — California. 



Distribution. — According to Holmes this species extends from Oregon to 

 Panama. The collections in the U. S. National Museum range from Drake's Bay, 

 California, to San Bartolome Bay, Lower California, and from Peru to Chile. 

 The intermediate region (from Lower California to Panama) is represented by 

 E. emerita (Fabricius), which occurs also on the Atlantic side of tropical America 

 (Eathbun). 



Bemarks. — 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. . . . 



Although occasionally found singly, Emerita is essentially a gregarious 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. . . . 

 For this reason collections often consist of females only, the smaller males being 

 regarded as young. Measurements of the carapace of 27 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 measurements of two 

 typical specimens: female, length of carapace 20.3 mm., length of telson 13 mm., 

 width of telson 6.9 mm., width 53% of length; male, length of carapace 11 mm., 

 length of telson 7.6 mm., width of telson 3.3 mm., width 43% of length. (Wey- 

 mouth and Richardson.) 



Biological Stirvey of San Francisco Bay. — There are only three 

 specimens of Emerita analoga in the bay collection : one, which was 

 apparently alone, was dug up in the sand on the beach skirting the 

 Presidio shore west of Fort Point ; another was obtained while seining 

 on the Fort Baker beach, and the third was taken, also in the seine, 

 on the beach west of Blunt Point, on the southern shore of Angel 

 Island. Owing to lack of more intensive sandy beach collecting no 

 definite statements can be made regarding the distribution and occur- 

 rence of this species in the region covered by the survey. 



Family Poecellanidae 



Body crab-like. Abdomen bent under and folded against the thorax; tail-fan 

 well developed. First pair of legs chelate, moderately elongate, stout; fifth pair 

 small and elevated so that they rest on the carapace. 



