374 MARINE INVERTEBRATES 



aperture. The Cerithiidce include a large number of genera, 

 mostly tropical in distribution. Their shells are usually highly 

 ornamented in various schemes of sculpture, but they lack beauty 

 in color. The animal is provided with a siphon, as is indicated 

 by the anterior canal of the shell. The operculum is corneous, 

 with a nearly central nucleus. 



GENUS Cerithium 



C. floridamim. A very common species on the west coast of Florida, 

 also sparingly found at Hatteras. It has eight or ten whorls, a grad- 

 ually tapering spire, and a sharp apex ; the aperture is oblong, with a 

 deeply cut anterior canal projected to the left and backward (when the 

 specimen is held apex up, with the aperture toward the observer). The 

 sculpture is elaborate, consisting of many rows of revolving ribs, and 

 close to the suture there are circling rows of nodes. There is a curious 

 hump just to the left of the aperture, which is quite characteristic of the 

 genus. The color is whitish-gray ; the length one and a quarter to one 

 and a half inches. Station, shallow water in lagoons and sheltered 

 spots. (Plate LXIX.) 



C. muscarum. Another Floridian species, somewhat smaller than 

 the last (one inch in length). It has heavy, prominent, transverse ribs 

 crossed by circling rows of chestnut spots, one heavy revolving rib 

 around the base ; eight or nine whorls ; a high-tapering spire ; and a 

 sharp apex. The aperture is oblong, with the anterior canal projecting 

 to the left. The columella is arched ; the color shining gray to very 

 light purplish. This very pretty little shell may be gathered literally by 

 the shovelful all along the west Florida coast in sheltered spots, on sandy 

 and shallow bottoms. (Plate LXIX.) 



C. minimum. A still smaller Floridian shell, with jet-black aperture 

 and anterior canal projecting horizontally to the left. The sculpture- 

 plan is of revolving ribs and a series of white granules just below the 

 sutures. Its station is the same as that of the last. Often the bottom 

 of a lagoon will seem to be literally paved with these somber-hued 

 little shells. From Tampa Bay to Charlotte Harbor they are very 

 abundant. 



GENERA Bittium, Triforis 



These are allied genera, having numerous species upon our 

 coasts, but the shells are so small that the inexpert collector is 

 not likely to notice them. Hosts of these minute, turreted, de- 

 cussated, blackish shells are to be found on the wiry grasses of 

 salt-marshes. They are also found on algae at low- water mark. 

 In Triforis the whorls turn to the left. Range from Cape Cod to 

 South Carolina, 



