OF CONCHOLOGY. 247 



appeared to be composed of fine transversely striate fibres, 

 disposed in wavy band.-;. They contained a smooth greenish 

 substance, resembling coagulated mucus, and without any trace 

 of organization, under a y*o Smith and Beck (55°) objective. 

 The specimens here described were obtained at Black Point, 

 San Francisco, in February. 



Var. nacelloides, Ball, (MSS. 1865). PI. 71, fig. 36 a-c. 



A very distinct variety of this species has exactly the aspect 

 of '■'' Nacella'' instahilis externally. It is of a blackish brown, 

 with sharp, radiating grooves sometimes obsolete near the apex. 

 Several shells beginning in this way have a margin with the 

 normal characters of O. pelta. It is quite distinct from the var. 

 montieola, Nutt., as described by Dr. Carpenter in the Amer. 

 Journ. Conch., Vol. II, p. 33, and might readily be taken for a 

 distinct species, as the sculpture differs entirely from that of 

 the normal pelta, which is sparsely furnished with prominent 

 bulging ribs. I am disposed to agree with Dr. Carpenter (Sup. 

 Rep. p. 533,) in referring A. pileolus, Midd., to " probably the 

 young of A. pelta ;" although I believe it impossible to determine 

 exactly what j»^Yeo/us really was. 



CoLLiSBLLA PATINA, Esch. sp. Plate 14, fig. 4. 



Acmcea patina, Esch., Zool. Atlas, V, p. 19, No, 7, pi. xxiv, 



f. 7 — 8. Cpr. Am. Journ. Conch, ii, p. 332. 

 Var. normalis, sive pintadina, (Gld.) 



Shell depressed, rounded, with a wide tessellated border, and 

 with the color in stripes or spots more or less tessellated ; sculp- 

 ture of sharp strioa. Soft parts : foot, mantle-edge and muzzle 

 dusky. Top of head, neck and thin part of mantle whitish. 

 Foot oval, thick, stout, sides quite smooth ; mantle smooth, with 

 a narrow thickened edge, ciliated, and with fine crenulations 

 corresponding to the striae of the shell ; head short, broad, 

 prominently bulging above. Tentacles moderate, pointed, stout, 

 greatly swelled at the base, with a prominent tubercle at the 

 inner corner of each. Muzzle transversely oval with an even, 

 puckered, scalloped frill ; disk entire, radiately striate, mouth 

 transversely oval. Eyes minute, on outer posterior bases of the 

 tentacles. Gill moderately long, subtriangular, with a strong 

 impressed line, forming a border on each side ; slightly attached 

 by posterior edges to the mantle above ; inserted on the under 

 surface of the hood, above the left side of the head and some 

 distance in front of the commissure between the mantle and neck. 

 Anal tubercle smooth, not very prominent, pointing to the right, 

 close to the right anterior end of the adductor; orifice internally 



