NOTES ON A COLLECTION OF SHELLS FROM TRINIDAD, 

 CALIFORNIA. 



By Eric Knight Jordan, 



of Stanford University, California. 



Trinidad Head, a lava promontory, lies about 28 miles north of the 

 city of Eureka, California. It projects into the sea in a southwesterly 

 direction, sheltering an area full of small volcanic knobs or intrusions 

 from between which the sea has washed away the intervening strata. 

 Conditions on the whole are decidedly ill adapted to the growth of 

 mollusks, even the small rocks scattered among the larger knobs being, 

 as a general rule, firmly embedded in fine, black, dirty, lava sand. 

 The situation is therefore very unfavorable to the growth of mussels, 

 abalones and other clear water species which abound elsewhere among 

 granite rocks along the whole coast of California. 



Directly in front of the village of Trinidad, however, there is exposed 

 at low tide a mass of rocks most of which may be overturned, revealing 

 many kinds of small shells. I took advantage of five low tides during 

 the past summer to collect in the above-mentioned area, finding in the 

 material taken two new species of Odostoirda and one of Turbonilla. 

 The following is a list of the species obtained by me. I am greatly 

 indebted to Dr. Paul Bartsch of the United States National Museum 

 for the determination of the minute forms. 



PELECYPODA. 



MYTILUS CALIFORNIANUS Conrad, 



Not found in the immediate vicinity of Trinidad; common on the 

 outer rocks. 



MODIOLUS FORNICATUS Gonld. 



Fairly common. 



PECTEN GIGANTEUS Gray. 



Abundant, young specimens especially so. 



PODODESMUS MACROCHISMA Deshayes. 



One upper valve. 



KELLIA LAPEROUSEI Deshayes. 

 CARDIUM CORBIS Martyn. 



Broken valves only. 



SAXIDOMUS GIGANTEUS Deshayes. 



Proceedings U. S. National Museum, Vol. 58— No. 2325. 

 181404— 21— Proc. N. M. vol. 58 1 I 



