1912.] NATURAL SCIENCES OF PHILADELPHIA. 455 



NEW POLYCLADS FROM MONTEREY BAY, CALIFORNIA. 

 BY HAROLD HEATH AND ERNEST A. MCGREGOR. 



The material serving as a basis for the present paper was collected 

 along the rocky beaches on the southern border of Monterey Bay 

 or was dredged in the shallow water off shore. That it does not 

 embrace all of the polyclads inhabiting this region is recognized, 

 but it probably includes the more common species, and will, it is 

 hoped, stimulate others to complete the list and extend their inves- 

 tigations into other localities bordering the western coast of North 

 America. It is a surprising fact that up to the present time, so far 

 as we can learn, but three species of these animals have been recorded 

 between Panama and the coast of Asia, a distance of over 7,000 

 miles. Stimpson's characteristically brief diagnosis of Leptoplana 

 maculosa is far from being exclusive, and accordingly must exist 

 as a nomen nudum. On the other hand, Miss Plehn's description 

 of Leptoplana calif ornica and Amblycereus luteus is accurate and 

 complete, as we know from specimens in hand. 



Concerning the habits of these animals, we have unfortunately 

 little to say on the subject. In captivity practically all of the 

 species fail to thrive, and if they live at all withdraw into some 

 shaded nook or remain quiet for hours together. In their native 

 haunts they are even more retiring, and observations upon their 

 mode of life are very difficult. Planocera californica occupies sites 

 farthest removed from low-tide mark. Under stones or in crevices 

 of the rocks it finds a hiding place and a food supply consisting of 

 small animals together with scant quantities of diatoms. Through- 

 out the greater part of the year its egg masses, forming more or less 

 circular patches from two to six millimeters in diameter, appear like 

 encrusting plant growths concealed in crevices of the rocks or attached 

 to the under surfaces of boulders scattered on the beach. About 

 mean-tide mark and even higher on the shore where the surf breaks 

 strongly, and from such situations down to the low-tide mark, 

 nearly all of the species of Leptoplana find a home. Leptoplana 

 rupicola was encountered upon two occasions only attached to the 

 under surface of large rocks at about the limit of extreme low tide. 

 This is likewise the habitat of Leptoplana timida and Stylostomum 

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