18 AMERICAN JOURNAL ' 



out further delay. They evidently moved about to obtain food, 

 and by some mysterious instinct returned to their stations before 

 high tide. The margins of the shells showed that they must 

 have been formed by the peculiar inequalities of the station 

 where I found them. Some of them had lost their way at times, 

 as the lines of growth showed, where sudden changes had taken 

 place in the curves of the margin where it touched the rock. 

 Some of them had assumed the most fantastic forms from this 

 cause ; one exactly resembled a planter's straw hat, and others 

 showed curious constrictions or expansions of the margin. 



In some cases one or more small ones were mounted on the 

 back of a larger individual, and there were erosions more or less 

 deep, of a circular form, of the diameter of the rider's foot. This 

 erosion was most extensive around the margin, which was often, 

 deeply excavated, while the central portion of the circle was 

 hardly eroded at all. It was probably due to the action of the 

 radula, as faint strioe might be distinguished by means of a glass. 

 In one case the indefatigable moUusk had gnawed through a 

 stratum of shell a quarter of an inch thick on the apex of an old 

 individual, which must have carried the incumbrance about for a 

 long time. The rocks exhibited no erosion. 



The species was originally described from the Gulf of Califor- 

 nia or Lower California, though by some misplacement of labels 

 the habitat was published as Valparaiso, in deep water. 



I found a few dead specimens on the same rocky beach. Dr. 

 Cooper and Mr. Rowell have obtained it from the Farallones, 

 Half-Moon Bay, New Year's Point, Santa Barbara and Santa 

 Catalina Islands. I have some small but exactly similar speci- 

 mens from Cape St, Lucas. Dr. Newcomb obtained this species 

 from Santa Cruz Island, 



The number of specimens examined while investigating the 

 anatomy of this species, is thirteen ; the number of shells which 

 have passed through my hands is about seventy-five. 



Gadinia carinata, n. sp. PL 4, figs. 12, 13. 



Testa rotundata, depresso-conica, tenui, alba, subpellucida ; 

 apice Isevi, subpostico et oblique marginem dextrum versus resu- 

 pinato ; superne, striis multis minutis versus marginem radianti- 

 bus ; intus Isevi, sulco cojispicuo munito, qui extus carinam va- 

 lidem format. Lon. 0*66, lat. 0-60, alt. 0*16 in. Animal 

 incognitum. 



Coll. Phil, Acad. Nat. Sciences. 



Hah. Aspinwall, Central America, Dr. E. Palmer. 



The thin depressed shell, fine striiTe, smooth and dextrally bent 



