78 THE WEST AMEKICAN SCIENTIST. 



MOLLUSKS OF SAN DIEGO.-V. 



The Calyptraeidae family contains the familiar cup-and- saucer and boat shells 

 so common on every ocean beach. Our spiny cup-and-saucer limpet, Crucibulu m 

 spmosum, grows abundantly on rocks and shells along our bay shores The shell 

 is irregularly round, conical, with a delicate internal cup-shaped lamina which is 

 attached along a Ime on one side to the inner wall of the shell. The boat shells 

 or crepidulas are similar limpet-like animals with an oval or oblong shell with a 

 posterior, generally lateral spiral apex; interior of the shell with a shelly lamina 

 covering its posterior half. Crepidula adunca grows to a length of an inch and a 

 half and is frequently found in large numbers attached to the shell of Norrisia It 

 IS easily distinguished from our other species by its prominent overhanging spire 

 and the delicate tmge of pink on beach-worn specimens. Crepidula rugosa is the 

 more common species, growing in abundance on scallops and other shells and rocks. 

 Crepidula navicelloides is a white elongated species found abundant in the inter* 

 lor of dead univalves, varying in size according to the shell occupied. Crepidula 

 dorsata var. lingulata is easily distinguished from the preceding by its oval shape. 

 It is abundant on rocks or shells, less than an inch in length, and very variable in 

 form. The horse-shoe Impet, Hipponyx, has a thick, obliquely conical, non- 

 spiral shell, with the apex somewhat posterior and curved backward. A shelly 

 base is secreted by the foot of the animal. Hipponyx tumens and H. antiquatus 

 var. serratus are the two kinds known at San Diego. 



The beautiful wentle-trap? or stair-case shells belong to the family Scalaridae 

 and are mostly pure white and lustrous. They are many whorled, turreted, and 

 ornamented with numerous transverse ribs. There are 150, mostly tropical, species 

 of Scalaria, many of them very rare and beautiful. Single shells of Scalaria pre- 

 tiosa have sold as high as $500. Scalarii i idianorum is the more common species 

 on this coast. I have also found Scalaria bellastriata, S. hindsii, and S. hindsii var. 

 subcoronata at San Diego, cli iging to alga-covered rocks on our ocean beaches, or 

 washed up on the sand. Other species are likely to be discovered as there are eight 

 kinds known on the coast. Opalia crenatoides is a shorter, stouter shell, easily 

 distinguished from the scalarias. 



The beautiful and fragile violet-snail, lanthina bifida, is frequently washed 

 ashore along the coast. The lanthina, or oceanic snails, are gregarious in the open 

 sea, where they are found in myriads, and are said to feed on the small blue aca- 

 lephae, Velella. When handled they exude a violet fluid from beneath the margin 

 of the mantle. 



The Caecidae are seemingly gregarious mollusks, that congregate in immense 

 numbers at certain seasons at least. The shell is tubular, regular, minute. The 

 following from the Proc. U. S. Nat'l Museum for 1885, p. 541, by Dr. Dall, gives 

 an -account of the only species known to me: 

 Caecum californicum, Dall. 



Caecum Cooperi, Cpr. Suppl. Rep. Br. As. 1864, p. 655, not 



Caecum Cooperi, Smith, Ann. Lye. Nat. Hist. N. Y., pp. 154, 168. 1862. 



