lOO CALIFORNIA ACADEMY OF SCIENCES. 



tion or transportation from one region to the other has 

 not been explained, but the aid of birds as carriers of 

 their eggs attached to their feet seems the most probable 

 explanation. For full lists and remarks on these regional 

 groups of species I must refer to W. G. Binney's works. 

 My object now is merely to refer to them as showing that 

 although many novelties cannot be expected, the most 

 productive regions near the south coast having been much 

 explored, still there is a large field yet to be visited which 

 may contain new forms. The scarcity of lime seems to 

 be one reason for absence of mollusca in man}' places. 



Mr. Bryant on former collecting trips obtained many 

 of the more northern species. The present small col- 

 lection picked up as they accidentally occurred between 

 Cape St. Lucas and La Paz, in the extreme south end of 

 the peninsula, shows both the narrow range of some 

 species and how they ma}' be overlooked unless specially 

 searched for. 



At Cape St. Lucas and for loo miles north, the large 

 and important collection of Mr. J. Xantus was made 

 in 1860-61, which furnished four new species of Bii- 

 limulus, besides the two South American forms. Two 

 others from towards La Paz are also contained in the 

 Academy collection. The Xantus' collection was made 

 during about two years' residence, and extended to Mag- 

 dalena Bay, but he gives also B. frotciis Brod., B. arte- 

 niisia and ^. xantusi Binn., as from Cape St. Lucas. 



Mr. J. Xantus (de Vesey) was employed by the U. S. 

 Coast Survey for 18 months, ending July, 1861. as tidal 

 observer at the Cape in 1859-1861, and from the nature 

 of his duties was not permitted to go a day's journey 

 from his post. He claimed in his letters to have gone 350 

 miles up the west coast, and also to have visited the high 

 mountains about 100 miles inland, besides La Paz, Masf- 



