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296 Genus Cavolina Abildgaard 1791 Shell squat, bulbous, horny-brown in color, characterized by a much constricted aperture, which is, however, very broad transversely. Sides of shell often prolonged into spine-like projections. Cavolinia is an alternate, incorrect spelling, and Hyalaea Lamarck is a synonym of this genus. Cavolina lojigirostris Lesueur Long-snout Cavoline Figure 64V Worldwide, pelagic. (47° N. to 40° S.). 5 to 9 mm. in length. Dorsal lip with a thin margin. Posterior portion of the ventral lip markedly projecting laterally. Common. Hyalaea li?nbata Orb. and H. angiilata Souleyet are synonyms. Cavolina gibbosa Rang Gibbose Cavoline Figure 64v Worldwide, pelagic. (43° N. to 38^ S.). About 10 mm. in length. Dorsal lip with a thin margin. Shell without appreciable lateral points. Ventral lip not more developed than the dorsal. Ventral surface with an anterior transverse keel. Common. Cavolina tridentata Forskal Three-toothed Cavoline Figure 64U Worldwide, pelagic. (40° N. to 40° S.). 10 to 20 mm. in length. Dorsal lip with a thin margin. Ventral Hp not more developed than the dorsal one. Shell without appreciable lateral points. The shell is as broad at the end of the lips as it is at the anterior end. C. gibbosa is narrower at the ends of the lips. Hyalaea afflnis Orb. is merely a form of this species. C. televms Linne might possibly be this species. Figure 64. The Pteropods or Sea-hut- Pelseneer;m,0/i7(?n77JCo/z/7;777e//irRang; terflies of American Waters, a, Spira- n, Creseis aciciila Rang; o, Styliola sub- tell a helicina Phipps; b, 5. lesuenri Orb.; zila Q & G; p, Creseis virgula Rang; q, c, 5. retroversa Fleming; d, 5. biilnnoides Hyalocylis striata Rang; r, Cavolina i?i- Orb.; e, S. trochiformis Orb.; f, Peracle fJexa Lesueur; s, Cavolina qiiadridentata bispinosa Pelseneer; g, Peracle reticidata Lesueur; t, C trispinosa Lesueur; u, C. Orb.; h, Spiratella infiata Orb.; i, Clio tridentata Forskal; v, C longirostris cuspidata Bosc; j, Clio reciirva Children; Lesueur; w, C. gibbosa Rang; x, C. im- k, Clio pyramidata Linnc; 1, Clio polita cinata Rang.