THE WEST AMERICAN SCIENTIST. 



MOLLUSKS OF SAN DIEGO. 



San Diego county forms the southern portion of the state of Cal- 

 ifornia. It is bounded on the east by the Colorado river, on the 

 south by the Californian peninsula and on the west by the Pacific 

 ocean Its fresh-water fauna is small, owing to the limited amount 

 of surface water and lack of running streams. We shall treat of 

 the few fresh-water mollusks in a separate paper. Its terrestrial 

 fauna is also limited to a few representatives in the sub-kingdom, 

 though of far greater interest than that of the fresh water. To the 

 marine fauna, therefore, we have to look for the greatest number 

 of representatives of this class, and we need not look in vain. 



From the present state of our knowledge we should consider that 

 the marine fauna of San Diego possesses a greater number of the 

 species of the Lower Californian coast than of the Californian prov- 

 ince of mollusks to the north, and that the true dividing line be- 

 tween the northern and southern faunas is at Point Conception. 



The beaches along the shores of San Diego bay are sandy or 

 muddy. Near the entrance is an extensive bed of clay and bould- 

 ers, known as La Playa, and forming the principal station for the 

 pholads, rock pectens (Hinnites giganteus) and other shells that 

 are not found elsewhere on our coasts in any number. The bay is 

 protected on the west by a high promontory, Pt. Loma, which has 

 a rocky ocean beach and a long shingle beach by the entrance to 

 the harbor. On the southwest, the bay is protected by a low, nar- 

 row peninsula, with a hard, sandy ocean beach. To the north of 

 San Diego lies a large lagoon known as 'False bay,' possessing ex- 

 tensive muddy flats and a narrow peninsula of sand dunes on the 

 west. North of the beach similar to that on the west of Pt. Loma, 

 rocky pools with irregular stretches of flat or broken boulders 

 partially imbedded in shell sand, beneath which a rich harvest of 

 minute shells may be gathered. It will thus be seen that San 

 Diego possesses a great variety of beaches, each prolific in certain 

 forms of marine life, as yet, but partially known to the world. 



A mollusk is an invertebrate animal, having a soft, fleshy body 

 (whence the name), which is inarticulate, and not radiate internally. 

 There are two subdivisions of this branch of the animal kingdom, 

 but this article will treat of the first only as the second division 

 contains minute or little studied animals which renders it impossi- 

 ble for them to be satisfactorily considered at present. Each of 

 these subdivisions is divided usually into three classes. 



The nautilus, the squid and the devil fish are of the first and the 

 highest class of mollusks, and distinguished from others by having 

 a distinct head with perfect eyes and a circle of arms around the 

 mouth, some or all of which are adapted for clinging. 



