CHAPTER XXXIII: THE BLIND SHELLS. 

 TUBE SHELLS 



Family C^cid.^ 



Shell minute, tubular, spiral at first, but becoming merely 



cylindrical, often losing the spiral part; one or more septa in 



posterior end of shell; foot short, bearing horny operculum; 



mantle thick, fleshy, circular; tentacles bear eyes; gill single. 



An interesting family of one genus of small mollusks inhabiting 



warm seas. 



Genus CAECUM, Flam. 



The strange development of this mollusk has been recently 

 investigated. " In the young of Caecum the apex is at first spiral 

 but as growth proceeds and the long tube begins to form, a septum 

 is produced at the base of the apex, which soon drops off. Soon 

 afterwards, a second septum forms a little farther down, and a 

 second piece drops off, leaving the shell in the normal cylindrical 

 form of the adult." — Cooke. 



Much confusion has been caused by conchologists who classi- 

 fied members of this genus at different stages of development in 

 \videly separate groups because they had no knowledge that 

 such changes of form occur in the life history of the individual. 



The Florida Blind Shell (C. Floridanum, Stimps.) is a 

 curved white horn of about thirty-two narrow rounded whorls. 

 The sinuses are wider than the rings. The posterior end is closed 

 with a septum bearing a sharp point. The mouth is oblique. 

 Length, J inch. 



Habitat. — Cape Hatteras to Florida. 



C. pulchellum, Stimps, I of an inch long, brownish, with 

 twenty-five rings and a blunt posterior septum, comes from 

 New Bedford, Mass., and neighbouring beaches. 



This "pretty blind shell" reveals its exquisite structure 

 under the microscope, though no larger than a grain of rice. 

 It does not escape the eye of the collector who is out for small 



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