BY A. KELLOGG, M.D. PTEROSTEPHANUS Kellogg. Involucre obconically-companulate; scales loosely imbricated in about two to three series; the exterior unequal, calyculate, suborbicular, oval, or oblong, obtuse; the inner series (of about eight) sub-equal, oblong-lanceolate, obtuse; scarious margins entire; (a broad, diffusely green line marks the centre). Receptacle naked, alveolate, alveoli, toothed. Achenia (mature wanting), oblong, sub-cuneate, or sub-obovate, somewhat compressed (?), slightly contracted at the crown, smooth, sub-pubescent above, on a short stipe. Pappus double; the exterior coroniform, persistent—a hyaline crateriform cup, with an even but minutely crenulate edge; interior of five (white) plumose, glabrous bristles, gradually dilating towards the base. Californian herbs, with runcinately, pinnatifid, radical leaves, and numerous naked scapes, bearing solitary, tigulate, yellow flowers; closely allied to _Malacothrix_ and _Calycoseris_, but with a plumose pappus. _P. runcinatus_ Kellogg. [FIG. 4.] [Illustration: FIG. 4.] Acaulescent, several naked scapes, two to four inches high, sub-glabrous, (rarely a few scattering glandular hairs); leaves radical, runcinately pinnatifid, lobes spinulose, frosty, or sub-wooly, pubescent, three to seven-nerved, short petioles winged, dilated at the base; rosulate, from a simple perennial somewhat fusiform root. Professor Whitney exhibited a new mass of meteoric iron, found near La Paz, on the Colorado River, in New Mexico, by Hermann Ehrenberg, Esq. A description and analysis will be furnished at a future meeting. REGULAR MEETING, APRIL 20TH, 1863. Vice President, Dr. Trask, in the Chair. Present, seven members. Philip Lutley Sclater, Esq., of London, England, was elected a Corresponding Member. Donations to the Cabinet: Three species of Reptiles from San Mateo, and one from Marin County, collected and presented by Mr. Bolander. Dr. Cooper communicated the following description of a new Californian Mollusc, discovered by Rev. Joseph Rowell, at Marysville, in the waters of Feather River. GUNDLACHIA Pfeiffer. _G. Californica_ Rowell. [FIG. 5.] [Illustration: FIG. 5.] Shell with the aperture sub-oval, obliquely expanded towards the left, posteriorly ronaded, and wider anteriorly. Internal shelf reaching forward about one-fifth the length of the shell, its margin slightly concave and oblique.