CLASS GASTROPODA 
245 
from one-fourth to one-fifth the shell’s length. Surface having radiating 
riblets and concentric growth-laminae, which are elevated into imbricating 
scales on the ribs; color gray or white, radiated with black. The form is 
oblong, sides subparallel or somewhat convex. The front slope of the cone 
is a trifle convex, the lateral slopes straight or a little concave, the posterior 
slope concave. The two sides of the fissure project upward in more or 
less salient points. The sculpture consists of alternately larger and smaller 
radiating riblets, crossed by sharp, concentric laminae, elevated into imbri¬ 
cating scales on the ribs. The blackish rays sometimes cover most of the 
surface, sometimes are narrow and few. Inside bluish-white, with a rather 
wide callus rim around the fissure; lateral edges blunt, ends slightly crenu- 
lated. In immature specimens the edges are crenulated. Length, 19; 
breadth, 10; height, \]/ 2 mm. (Tryon and Pilsbry, Manual of Con - 
chology .) 
Type in United States National Museum. Type locality, Monterey. 
Range. Bodega Bay, California, to Magdalena Bay, Lower California. 
Fossil: Pleistocene, San Pedro to San Diego, California. 
Described as Clypidella callomarginata. 
Genus FISSURELLA Bruguiere, 1791 
Shell oval, conical, depressed, with the apex in front of the center, and 
perforated; surface radiated or cancellated; muscular impression with 
the points incurved. In very young shells the apex is entire and subspiral; 
but as the perforation increases in size, it encroaches on the summit, and 
gradually removes it. (Tryon, Structural and Systematic Conchology.) 
Type. F. picta Gmel. 
Distribution. Universal, but mostly in warm seas. 
Fissurella volcano Reeve, 1849 
Conchologia Iconica, Fissurella, fig. 2. 
Fiss. testa ovato-conica, antice vix attenuata, radiantim costata, costis 
rudibus, inaequalibus, hie illic majoribus, orificio oblongo; albida, roseo 
radiata radiis nigropunctatis, interdum rosea, purpureo-radiata, circa ori- 
ficium nigropunctata. (Reeve.) 
Shell ovately conical, slightly attenuated, anteriorly rather thick, radi- 
ately ribbed, ribs rude, uneven, here and there larger, orifice oblong; whit¬ 
ish, rayed with rose, rays dotted with black, sometimes rose, rayed with 
purple, black-dotted around the orifice. (Reeve.) 
Type in Museum Cuming. Type locality, Santa Barbara, California. 
Range. Crescent City, California, to Panama. 
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