ii8 SOUTHERN , CALIFORNIA ACADEMY OF SCIENCES. 



the decay of the original plants. These preserve only the form 

 and the exterior characters of the original. See PI. i and 2. 



Plate 2, from a photograph taken on San Miguel Island, one of the 

 islands forming the southern line of the Santa Barbara Channel, on the 

 coast of California, shows the casts of trees which were probably killed 

 by volcanic agency, and afterwards decaj-ed, surrounded by shells of dead 

 snails of a nearly extinct species. The molds formed by the decay of the 

 trees were filled with drifting sand and cemented by mineral substances 

 held in solution by the water which permeated the surrounding soil. 



The soil was subsequently carried away by the prevailing winds, leav- 

 ing the casts as shown in the illustration. Tlie reason for this was that 

 after the advent of the whites thousands of sheep and cattle were turned 

 loose upon the island and increased so rapidly that they eventually de- 

 stroyed large areas of the vegetation which had protected the surface from 

 the disturbing agencies of the elements ; the soil thus exposed was carried 

 away by the wind and rain and the surface covered by drifting sand. 



The land snails thus deprived of the succulent vegetation upon which 

 they had subsisted, perished by millions, leaving acres upon acres of ground 

 covered with their dead shells, as seen in the illustration. 



These shells (Helix Ayresiana) are foun only on the islands of San 

 Miguel, Santa Rosa, Santa Cruz, and one or more of the Anacapas, where 

 the "sheep and cattle industries" have nearly exterminated them, thus il- 

 lustrating the effects of the destruction of the vegetaion upon some of the 

 forms of the animal life of a region. 



Twenty-five years ago the writer found extensive areas of the same 

 character on Santa Rosa Island, the casts of trees were then standing, and 

 the ground was covered with dead snail shells in greater abundance than is 

 shown on this illustration. 



(To be Continued.) 



Sphaerostigmat erythra, n. sp. 



BY A. DAVIDSON, M. D. 



Annual, slender, upright, branching freely 6 in. to i ft. high, 

 whole plant minutely puberulent and glandular throughout, stem 

 generally purplish especially in the taller specimens, epidermis 

 not flaking: lower leaves ovate-lanceolate 1 \.o lyi inches long, 

 % inch wide, tapering to petiole, slightly repand-denticulate, 

 midrib prominent beneath; floral leaves similiar, above entire and 

 much smaller; petioles of radical leaves i in. long, those of the 

 lower cauline ]4: inch.: flowers numerous, axillary, minute, 

 petals I line long, light red becoming darker in age: sepals reflexed 

 in flower, calyx finely puberulent and glandular, tube obconic 

 very short; capsule 2 in. long, ^ line broad, obtusely angled, 

 slightly curved with almost truncate tip, sessile, not adnate to 

 the leaf. 



In habit, this plant somewhat resembles S. strigulosa 

 T. & G. but in foliage and flower it is quite different. Collected 

 by the author in April, 1900 on the rocky slope of the San Fran- 

 cisco River near Clifton, Arizona, at an alt. of 3,500 to 3,800 ft. 



.No. 244. Los Angeles. 



