82 atherinidve: silversides 



Amer. Mus. Nat. Hist., 35, 155, 1916; Jordan, Copeia, No. 56, 46, 1918; 

 Barnhart, Cal. Fish and Game, 4, 181, 1918; Thompson, Bull. Cal. Fish and 

 Game Comm., No. 3, 1-29, figs. 1-9 (babits), 1919; Higgins, ibid.. No. 5, 156, 

 1919; Thompson, ibid. 201, 203. 



Type-locality. — San Francisco Bay. 



Leuresthes crameri Jordan and Evermann, Bull. U. S. Nat. Mus., 47, pt. 1, 802. 



Type-locality. — Ballenas Bay, Cape Abreojos, Lower California. 

 Osburn and Nichols (1916) and Jordan (1918) seem to have 

 demonstrated the identity of Leuresthes crameri with L. tenuis, the 

 form called crameri living in the open sea, the original tenuis in San 

 Francisco Bay. The alleged difference in size of the scales does not hold. 

 The remarkable spawning habits of this species, locally known as 

 the "Grunion," although popularly well known, were first mentioned in 

 scientific literature by the junior author in 1916. Subsequently Mr. 

 Percy S. Barnhart observed and reported in some detail on the phe- 

 nomena, but it has remained for Mr. Will F. Thompson to deter- 

 mine the nature of the marvelous adaptations and adjustments involved. 

 It appears that in six months of the year, chiefly March, April, May, 

 and June, just after the crest of the latter high tides of the full-moon 

 series, the grunion leaves the surf in large numbers, being washed 

 high on the beach by the largest breakers. The eggs are then fertilized 

 and laid well down in the sand, where they are covered still deeper by 

 the deposition of sand which takes place on this level of the beach only 

 during the complex of tide conditions noted above. 



"The story concluded by the escape of the larvae into the surf com- 

 prises one of the most marvelous of the many strange chapters in the 

 life histories of fish. It is eloquent of exquisite adaptation to a seem- 

 ingly minor physical phenomenon — the erosion of the beach by one part 

 of a wave, and its upbuilding by another. Those waves are made use 

 of which carry the fish high on the beach ; those parts of the tide are 

 utilized which allow the pods of eggs to be laid without risk that 

 further rise of the tide will carry the eroded area over them; the runs 

 occur during those nights in a series which are the last available, 

 because of their height, thus eliminating in so far as possible the danger 

 that unusually rough weather will sweep away the eggs; and the eggs 

 are laid during those series of the tides which will allow the escape 

 of the larva two weeks later. The larvae themselves do not hatch until 

 the sand over them is swept away, even though a month pass by; but 

 when the time comes and the waves of the high tide wash over them, 

 eroding the surrounding sand, they are ready to escape. The eggs 

 are laid in what is nearly dry land, or moist soil, a fact which has no 

 parallel in our knowledge of marine fishes. They are subject to attack 

 by terrestrial enemies, but escape the far more numerous marine enemies. 

 Indeed, so advantageous to the species are these adaptations that the 



