16 PROCEEDINGS OF THE ACADEMY OF [1819- 



ON THE LAND SHELLS OF THE MEXICAN ISLAND OF GUADELTJPE, 

 COLLECTED BY DR. E. PALMER. 



BY W. G. BINNEY. 



The island of Guadelupe is about 220 miles from San Diego, off 

 the west coast of Lower California. Its molluscous fauna has for 

 the first time been made known by the researches of Dr. Edward 

 Palmer, who visited it in 1875. He found numerous fragments of 

 snail shells which had been devoured by a species of mouse, the 

 only inhabitant of the island. These fragments appear to belong 

 to Arionta Roivelli, Newcomb (see L. & F. W. Sh. of N. A. I. p. 

 185), a species found in Lower California. Some perfect shells 

 were found, among them a smaller variety. Arionta facta, Xew- 

 conib, was also found, the variety with open umbilicus, like that 

 form found fossil on San Nicolas Island, California. 



The most interesting discovery, however, is that of living spe- 

 cimens of Binneya notabilis, a species found also on the California 

 island of Santa Barbara. There is strong reason for believing 

 the Mexican genus Xanthonyx to be synonymous with Binneya. 

 We may suppose, therefore, that from Mexico the genus has been 

 introduced by the usual means of distribution to this island of 

 Guadelupe, and thence to Santa Barbara. Thus, its presence on 

 the latter island is accounted for, which was not the case when 

 we had only the mainland of California to look to, as its absence 

 there has been proved. So, also, in the case of Arionta, facta, we 

 ma3 T account for its distribution by supposing it to have been in- 

 troduced from some unknown locality on the mainland to Guade- 

 lupe first, and thence to the California islands. 



The specimens collected are in the Museum of the Boston 

 Society of Natural Histoiy. 



Four species of Orthoptera were collected also. One of these 

 is shown by Dr. Scudder to be identical with a Mexican species, 

 and two of the others have also been found at San Diego. 



