On March 9, 1937, a harbor porpoise (Phocaena phocoena) that had been found dead the previous day on Rockaway Beach, San Mateo County, California, was brought to the Department of Mammalogy, California Academy of Sciences, by Mr. William Sommers. This animal, a young female, measuring about 40 inches in total length, was believed to have expired not more than a few minutes prior to the time that it was found. The cause of death was quite apparent. The tail of a small shark (Mustelus californicus) protruded about 2.5 inches from its mouth. Upon dissecting the porpoise the shark was discovered to be 22 inches long, its head being partly within the stomach of its captor. Obviously the shark had become so firmly lodged in the esophagus of the mammal that breathing was prevented. The lungs of the porpoise were filled with froth, indicating that suffocation had occurred. Apparently this young marine mammal had misjudged the size of its prey.