2 University of Michigan 



with the aid of a camera lucida, and all are magnified approx- 

 imately thirty-three diameters, except figure 8, which is mag- 

 nified i6 times. 



It would be interesting to make an opening in each whorl 

 of the shell and trace the lamellae to the apex, but the delicacy 

 of the operation and the small number of specimens available, 

 except in the case of C. exigmim, have made it inadvisable to 

 attempt this at present. 



I wish to express appreciation of the interest of Dr. Clapp 

 and Dr. Walker, who have loaned and given specimens and 

 offered helpful advice and criticism. 



It may be stated in general that the lamellae of Carychium 

 are two in number, the lower one arising as a tubercle on the 

 columellar margin of the aperture, the upper appearing as a 

 more conspicuous projection upon the parietal wall. The 

 lower fold is the smaller and revolves about the columella 

 beneath the upper lamella, which attains its greatest develop- 

 ment within the body whorl of the shell. The edge of each 

 lamella is thickened, cord-like. The degree of development 

 of the lamellae is undoubtedly correlated with the age of the 

 shell. In fresh young specimens they are well developed but 

 not so heavily corded; in old shells they seem to be smaller, 

 probably somewhat worn. There is also considerable varia- 

 tion in the degree of sinuosity of the lamellae, although within 

 such limits that they remain specifically distinct. Clapp has 

 pointed out (Nautilus, XIX, p. 138, 1906) that the shells of 

 each species vary considerably in size, and it is to be expected 

 that the lamellae will also vary accordingly, although it will 

 be seen from the following notes that there are dififerences 

 between species so marked as to be of importance. 



