MOLLUSOA of FORTH rich. 
365 
Subgenus Atys s. s. 
Atys g-uildinii Sowerby. 
Atys rjuildwii Sowerby, Conch. Icon., ivii, pi. V, fig. 26, 1869. 
Shell inflated, thin, dull grayish white, attenuated into a rounded ridge above, where it is perfo- 
rated or dosed, umbilicated below; wrinkled with growth lines and spirally striate, especially at ends, 
where it is sometimes reticulated; outer lip decidedly elevated above; columella thin, slightly folded. 
Length, 8; diameter, 5 mm. 
Mayaguez Harbor, Porto Rico, one specimen; Ensenada Honda, Culebra, one shell. 
Atys Sander soni Dali. 
Atys? sandersoni Dali, Bull. Mus. Comp. Zool., ix, p. 99, 1881; Blake Rep., ii, p. 54, pi. xvii, fig. V, 1880. 
Shell thin, polished, translucent white, with the aperture longer than the axis of the shell; 
growth lines faint; spiral sculpture consisting of about a dozen lines at each end of the shell, becoming 
faint or obsolete at center; vertex having a deep pit, from the center of which the margin of outer 
lip arises; columella nearly straight, reflected over the umbilicus and closing it, or only leaving a chink. 
Length, 4; diameter, 2 mm. 
Two young specimens were obtained in Mayaguez Harbor, Porto Rico. 
( Anaspidea.) 
Tectibranchs without a fleshy head shield. 
Family APLYSIID2E. 
Animal not protected by a shell, the neck and head narrower than the body ; mouth a vertical 
fissure; two tentacular folded lobes above the head; two elevated rhinophores behind these, in front 
of which are the small eyes. Pleuropodia curved over the back forming two lobes inclosing mantle 
and gill. Genital orifice within the dorsal slit; shell nearly or quite covered by the mantle, a mere 
concave plate. 
Subfamily APLYS1NA2. 
Genus TETHYS Linnaeus, 1758. 
Pleuropodia arising in front of the middle of the animal’s length, free, used as swimming lobes, 
mantle nearly covering the gill, having a median tube or orifice produced behind in a lobe or lobes 
forming an excurrent siphon; foot well developed; shell thin, with pointed, small apex, and having 
a concave posterior sinus. 
It is better known under the generic name of Aplysia. 
Tethys protea Rang. 
Aplysia protea Rang, Hist, Nat, Apl., p. 56, pi. x, figs. 1-3, 1828. 
Back much swollen; swimming lobes large; neck slender; tail pointed; foot large; surface 
generally covered with scattered, ring-shaped, dark markings. 
Length, from 4 to 16 cm. 
Ensenada Honda, Culebra Island.; Ponce Reefs; San Antonio Bridge, San Juan; Mayaguez; reefs 
at Guanica, Porto Rico; Caballo Blanco Reef, Vieques. 
This form varies greatly in color, and among our numerous specimens as to size, some of which 
are probably young. In certain specimens the rings of color are heavy and distinct; in others there 
is scarcely a tint of the dark rings and there is every variation between. The inner sides of the 
pleuropodia and the mantle are variously marked with dark patterns of color. 
Tethys cervina, n. sp. Plate 56, tig. 2. 
Body elongated, flabby; mouth encircled by thick lips; tentacles short; eyes inserted in front 
of the tentacles. Swimming lobes thick, united behind at some distance in front of the hinder 
extremity; mantle orifice minute; mantle ending behind in a small fold; foot narrow, nearly smooth. 
Colors: The body is a lurid gray overlaid with reticulations and blotches of darker color. It also 
has scattered, small, nearly round, smoky brown spots throughout its surface. The foot is smoky 
