^E. officinalis^, variety ^rotunda^. Usually massive; attached by a broad base; sides vertical; oscula large and conspicuous on top, or small in longitudinal rows on the sides. In the young this variety may have a conical form with only one orifice, but later it has several oscula. Its rotundity of form increases with the number of large orifices, but in the adult stages the form varies, some being conical, while others have the top divided into radiating ridges. ^E. officinalis^, variety ^dura^. Irregular, massive, horizontally expanded, with conical process on upper surface. GENUS ^Hippospongia^ ^H. equina.^ Some of the sponges of this species are massive, spherical, and attached by a small base; others are horizontally expanded or cake-shaped; some have a depression in the upper surface and become cup-shaped. ^H. equina^, variety ^cerebriformis^. Massive, circular, cake-shaped, often depressed in the center, producing a cup-shape, attached by broad base; surface broken up by parallel longitudinal ridges having many tufts. Cup-shaped forms predominate, and have a more or less rough surface. This is one of the species known as grass-sponges. ^H. equina^, variety ^meandriformis^, the velvet sponge. The surface of this variety has a protruding flattened cushion of fiber which slightly resembles the convolutions of the brain-coral. Sometimes these cushions are extended into long pencils. The oscula are large and ragged on the edges; the shape is irregular. The average size is seven to eight inches in diameter. (Plate XL.) ^H. equina^, variety ^elastica^ (variety ^agaricina^, Hyatt), the yellow sponge. This is the second grade of commercial sponge, corresponding to the Zimocca sponge of the Mediterranean. It is found growing with the "sheepswool" in a depth of two to twenty feet, and is abundant. It is massive and cake-shaped. The whole surface is a network covered with numerous small, fine cones. (Plate XL.) The variety ^dura^ is classed with this species, which it resembles in appearance, though it is harder in texture. ^H. canaliculata.^ Massive, frondose; more or less horizontally expanded; bears finger-like processes of varying development on the upper surface. ^H. canaliculata^, variety ^gossypina^, the sheepswool sponge. This is the highest grade of the commercial bath-sponge. It is called "sheepswool" because, perhaps, of its irregular shaggy surface. It is covered with tufts, the larger oscula occupying the intervening depressions. [Illustration: PLATE XL. Euspongia officinalis, var. adriatica. Hippospongia equina, var. meandriformis. Hippospongia canaliculata, var. gossypina. Hippospongia equina, var. elastica. Euspongia officinalis.]