TETHYS. 113 
Aplysia nigromarginata Risso, t. c., p. 875, and Hist. Nat. Eur. 
Mérid., iv, p. 43. 
Aplysia lutea Risso, J. Phys., p. 375, and Hist. Nat., p. 43. 
All described from the vicinity of Nice, and none of them recog- 
nizable with certainty. 
Aplysia unicolor Blainville, Dict. Se. Nat., xxvi, p. 327 (1828) ; 
Journ. de Phys., Vol. 96, f. 9,10. Bayonne, Toulon, Ocean coast 
of France. Not recognizably described. 
Aplysia petersonii Gray. Body contracted posteriorly, and 
divided transversely into two portions. Head very large, depressed 
smooth. Foot very broad, deeply emarginate in front, expanded 
beyond the edge of the body; the part beneath the hinder portion 
of the body divided by deep wrinkles into distinct tubercles. Mouth 
sunk in, large; labial expansions short, triangular, wrinkled. Ten- 
tacula situated half way between the head and the transverse con- 
traction, short, conical. Body subglobular, externally tubercular, 
wrinkled. Lobes of. the mantle rounded, united behind, the right 
one rather longer than the left, partly covering the shield. Shield 
partly exposed, ovate; nucleus submedial; columellar edge sub- 
angularly bent. Length 5 inches, breadth 24 inches. ( Gray.) 
This species constitutes a peculiar section of the genus, character- 
ized by the transverse contraction of the body. The animal figured 
in Seba, iii, t. 1, f.8, 9 (Aplysia sebe, n.) appears to belong to the 
same section. It differs from the foregoing species in the form of 
the hinder part of the foot, ete. (Gray Spicilegia Zoologica, pt. I, 
p. 4, pl. 4, f. 4, 4a (one-half nat. size). July 1, 1828.) 
Marseilles (Peterson esq.). 
I am disposed to think this a peculiarly abnormal specimen of 
Tethys leporina. It was evidently described from an alcoholic exam- 
ple. Type said to be in Brit. Mus. Sowerby’s later A. petersoni (see 
p. 70) is not the same. 
Aplysia sebe Gray, Spicil. Zool., p.5 ; Seba, Locupletissimi Rerum 
Naturalium Thesauri, etc., iii, p. 4, pl. 1, f. 8,9. Gray’s informa- 
tion on this is contained in the last paragraph of his description of 
A. petersoni (see above). On referring to Seba’s portly folio I am 
quite ready to endorse his opinion that the creature pictured is a very 
singular marine monster; but my Aplysia lore does not enable me 
to name it. 
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