74 THE NAUTILUS. 



specific characters had not been established nascent species, 

 in fact. Marquis de Folin published a monograph of the family 

 but I have never been able to refer to his memoir. So far as I 

 can learn it is not to be found in any scientific library in the 

 United States. Tryon in preparing his Manual of Conchology 

 has been equally unfortunate. He was unable to obtain the 

 memoir. Agents of the Philadelphia Academy of Sciences in 

 Europe were specially instructed to obtain the work but without 



success. 1 



Tryon in his Manual presents two plates of figures of Caecum 

 depicting thirty-nine species. I have compared my forms with 

 these figures and under the names given have presented a few 

 drawings of these forms which more or less resemble the figures 

 as given by Tryon. 



The family Caecidae consists for the most part of minute 

 tubular shells from one to two millimeters in length. These 

 shells are slightly curved backward. The earliest stage shows 

 a closely coiled shell discoid in form ; after a few symmetrical 

 whorls it abruptly straightens out into a tubular shape and ag 

 the shell grows the coiled nucleus is discarded, leaving a tubular 

 shell which in many species is also discarded after the perma- 

 nent shell begins to form. The end exposed after this separa- 

 tion is closed by a plug, or septum having a form which may 

 be ungulate, mucronate or mammillate. The tubular shell may 

 be smooth, longitudinally ribbed or transversely marked by 

 encircling ribs, these annulations being more or less prominent 

 and crowded. They vary in color from a light brown to a 

 chalky white resembling a dead shell, though often preserving 

 the operculum. When smooth the shell is often hyaline. 



If one desires specimens of this interesting group he may 

 usually find them in the sand which drops out of sponges kept 

 in a druggists' box or drawer. 



It must be understood that the following designations do not 

 imply that I regard the forms as representing the species as- 

 signed to them. Doubtless some of them are different; but re- 



1 De Folin' s work, " Les Fonds de la Mer,' ' is now contained in the library 

 of the Academy. 



