It was observed, at the localities alluded to, usually flying in company with the western Gull, _Larus occidentalis_, Audubon, a large and handsome species, of which, in a future part of our work, we hope to have the pleasure of presenting a figure and description to our readers. It appeared to be engaged in the capture of small fishes, of which several species abound in the harbor of San Diego, and also appeared to feed on the small maritime animals of various classes, that inhabit the immense beds of _Kelp_ which occur on the coast, and are especially extensive off the harbor of San Diego less than a mile from its mouth.[1] The nests and eggs of both the present species and of the western Gull were found by Dr. Heermann on the Coronadoes islands which are situated a short distance below the mouth of the harbor. Our first notice of this bird which we regard as having been previously undescribed, and which we dedicated to its discoverer, is in the Proceedings of the Academy of Natural Sciences of Philadelphia, Vol. VI. p. 187, (October, 1852.) The figures given in the present plate are about one-sixth of the natural size. DESCRIPTION AND TECHNICAL OBSERVATIONS. Genus Larus. Linn. Syst. Nat. I. p. 224, (1766.) Larus Heermanni. Cassin. Proc. Acad. Nat. Sci., Philada., Vol. VI. p. 187, (1852.) Form. Bill rather long and slender; wings very long, extending beyond the end of the tail; first primary longest; tail truncate or slightly emarginate. Dimensions. Adult. Total length of skin from tip of the bill to the end of the tail, about 17½ inches; wing, 13½; tail, 5½; bill from the angle of the mouth to the tip of the upper mandible 2½ inches. Colors. Adult. Bill red, both mandibles tipped with black; feet and legs dark; head white, which color gradually blends into an ashy lead color enveloping the entire body above and below—darker on the back and wings and paler on the abdomen. Secondary quills tipped with white, forming an oblique bar when the wings are folded. Superior coverts of the tail very pale cinereous, nearly white. Quills and tail feathers brownish black, all of the latter narrowly tipped with white. Shafts of the two first primaries white on the inferior surface of the wing. Young. Smaller, total length about 16 inches, wing 13, tail 5 inches. Entire plumage brown, darker on the head and paler on the under surface of the body; quills and tail feathers brownish black, the latter narrowly tipped with white. Hab. Coast of California. Spec. in Mus. Acad. Philada.