MOLLUSCA OF PORTO EICO. 
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Family ANCYLID.E. 
Genus ANCYLUS Geoffroy, 1767. 
Ancylus obscurus Haldeman. 
Ancylus obscurus Haldeman, Monog. Limnseidse, p. 9, pi. i, fig. 3, 1844. 
Humacao, Porto Itico (Crosse); St. Thomas; Jamaica; eastern United States 
Ancylus beaui Bourguignat. 
Ancylus beaui Bourguignat, Journ. de Conchyl., iv, p. 176, 1853. 
Ancylus beaui Clessin , Chemnitz, n. ed., p. 69, pi. vn, fig. 10. 
Near Luquillo, Porto Rico (Crosse) ; Guadeloupe. 
Family PHYSIDiE. 
Shell spiral, thin, horn-colored, sinistral; outer lip simple, sharp; tentacles acute, elongate; 
dentition complex. 
Genus APLEXA Fleming, 1828. 
Shell sinistral, thin, brilliant, apex pointed; whorls but slightly rounded; aperture somewhat 
elongated; columella slightly twisted. 
Type, Physa hypnorum Linnseus. 
Aplexa sowerbyana d’Orbigny. Plate 54, fig. 11. 
Physa sowerbyana d’Orbigny, Moll. Cubana, I, p. 190, pi. x, figs. 11, 13, 1842. 
Shell oblong-ovate, polished, dull amber, lighter when young; spire elevated, acuminate; colu- 
mella thin, slightly tortuous. 
Length, 14; diameter, 8 mm. 
Rio Caguitas, Caguas, Porto Rico. A number of young specimens were obtained. Also found in 
Cuba, Jamaica, St. Thomas, and Guadaloupe. 
Suborder STYL0MMAT0PH0RA. 
Superfamily DITREMATA. 
(VASOPULMONATA. ) 
Family ONCHIDIIDJE. 
Genus ONCHIDELLA Gray, 1850. 
Animal with the dorsal surface nonpapilliferous, ovate, leathery, with no shell in the adult state; 
respiratory orifice above and on right side of vent, genital orifice to right of tentacles. 
Type, 0. nigricans Quoy & Gaimard. 
Onchidella floridana Dali. 
Onchidium floridanum Dali, Proc. U. S. Nat. Mus. 1885, p. 288. 
Onckidium ( Oncidietta ) transatlanticum Heilprin, Proc. Acad. Nat. Sci. Phila. for 1888, p.327, pi. 15, figs. 4, 4a; Pilsbry, Trans. 
Conn. Acad., x, p. 503,1900. 
Guanica, Porto Rico; Knights Key, Florida; Bermuda. 
This form is stated by Sir Charles Eliot, of the British Legation, to be almost indistinguishable 
from 0. nigricans Quoy & Gaimard, which he collected abundantly at Auckland, New Zealand. One 
specimen was obtained at Guanica by the United States Fish Commission. 
Family VERONICELUDhE. 
Genus VERONICELLA Blainville, 1817. 
Body long, without shell or furrow above the margin of the foot; moderately rounded above, 
flattish below, the sole divided longitudinally into three areas by impressed lines; nocturnal. 
