MACROCERAMUS. 



221 



Cylindrella pontijjca, Gould, Proc. Bost. Soc. Nat. Hist. Ill, 40 (1848) ; 



Terr. Moll. IJ, 306, pi. Ixix, f. 1.— Chexp, Man. de Conch. I, 446, f. 



3305, 3306 (1859). 

 Macroceramus poniijicus, W. G. Bixney, Terr. Moll. IV, 137. 

 Macroceramus kieneri, Pfeiffek, Mon. Hel. Viv. IV, 689. 



Florida, from Tampa Bay to Key West. Also Cape Florida 

 and Key Biscayne. Also Cuba. 



When in motion, the axis of the shell is parallel with the line 

 of progress, and lies almost horizontally. The rapidity with 

 which the animal moves is quite surprising. The advance seems 

 to be effected in this way : The posterior point of the disk of the 

 foot, being detached from the object on which it rests, is carried 

 forward by muscular contraction and again fixed, leaving a curve 

 between the attached point and the next anterior part of the 

 disk, which is not yet detached. This operation is continued 

 throughout the whole disk, every part of which becomes succes- 

 sively detached, curved upward, and again attached, from the 

 extremity to the snout, exhibiting in action a curved or wavy 

 motion, or undulation, commencing at the extremity, proceeding 

 rapidly forward, and terminating at the head. But before one 

 muscular wave is exhausted at the head, another has begun to 

 flow; so that two series of undulations are visible at one time. 

 With this double alternation of action, the body is propelled with 

 a rapidity greater than can be attained by the more common, 

 gliding motion of the Helices. During motion the eye-peduncles 

 are extended, and remain steadily in one position. 



They are found in woods, on the ground, under leaves, but are 

 not very plentiful. The most northern point where they have 

 hitherto been noticed is Tampa. On the eastern shore of the 

 peninsula, they occur at Cape Florida, and ako at Key West and 

 Key Biscayne. 



Macroceramus gossei, Pfeiffer. — Shell Hmate, tnrrito-cylin- 

 drical, obliquely ribbed, whit«, opaque, with semilunar blotches and 

 pellucid, horn-colored spots ; spire cylindraceous, apex attenuated and 

 acute ; suture crenulated ; whirls eleven, convex, the last about one-fourth 

 the length of the shell, rounded, subangulate at base ; aperture sub- 



