THE WEST AMEEICAN SCIENTIST. 63 



MOLLUSKS OF SAN DIEGO.-IV. 



The Mitridae family is represented on our coast by a single species of the genus 

 Mitra (M. maura, Swains), dead shells of which are often washed ashore on the ocean 

 beiches. It is a deep water shell and possesses a smooth black epidermis. The shell 

 attains a length of two inches or more, is fusiform in shape, and is quite solid. 



The shells of Marginellidse are porcellaneous, polished, usually smooth or with 

 longitudinal ribs, covered by the mautlelobes of the animal and devoid of epider- 

 mis, thus resembling externally the cowries and olives. 



Erato has a short, conical, distinct spire and linear aperture, Both of our San 

 Diego species, vitellina (Hds.), and columbella (Mke.), are quite rare; the former 

 rather more than a half -inch long, and dull reddish -brown above; the latter usually 

 less than a fourth of an inch long and of a delicate brown, greenish or flesh-color, 

 and with a more prominent spire than vitellina. 



Our marginellas are all minute and probably abundant on sea-grass or algae at 

 certain seasons. Carpenter's regularis has been found abundant but his slightly larger 

 subtrigona has not as yet been found so. The minute Volutella pyrifonnis, Cpr., 

 has also been found on sea-grass in the bay of San Diego. The pret ily-marked Vol- 

 varina varia, of Sowerby, is found abundantly beneath rocks partially imbedded in 

 shell sand, in company with other small shells, ophiurans, and other marine animals. 

 It is about three lines long, of a delicate flesh-color and irregularly marked with 

 wide or narrow bands of reddish-brown. 



The Olividae are mainly tropical, brilliantly colored, solid, and smooth, polished 

 shells without epidermis. The well-known and beautiful tent shell, the rice shells 

 of the West Indies, and many others are familiar to many who are not conchologists, 

 and valued for their great beauty. The only members of this family on our coast, 

 are olivella boetica, a small slender shell, a half inch long, with grayish markings, 

 and the familiar 'Indian money shell 'of the Pacific coast, Olivella biplicata, a larger, 

 thicker shell (an inch long and J inch in diameter), varying in color from white to 

 black, but usually of a purple tint and stained with brown. 



Columbella fuscata, a single specimen of which was found on sea-grass in the 

 bay of San Diego, is an extra-limital species of the sub- tropical family, Columbel" 

 lidae. Our other members of this family are small and mostly inconspicuous. As* 

 tyris carinata, and its variety Hindsii, are found abundantly on sea-grass during the 

 spring near the entrance to our bay, and are very variable in form and coloring. As- 

 tyris tuberosa is often found washed up along the bay .shores, but not alive. Ana- 

 chis subturrita is another small shell found among oyster shells on wharf-piles, and 

 probably elsewhere, below low-water mark. 



The last of this family to be mentioned is a species of Amphrissa (A. versicolor), 

 a genus peculiar to West America. The shell is about a half inch long, slightly in- 

 flated, strongly corrugated and very variable in color, usually grayish or more or less 

 marked with brown or of a bright red throughout. It is found with Volvarina and 

 is not rare. 



The terebras are known by their long, narrow, many-whorled shells, with small 

 aperature, notched in front, and no true columellar plaits. Carpenter's Myurella 



