386 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



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 successively detached, curved upward, and again at- 

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

 motion, or undulation, commencing at the extremity, proceeding rapidly for- 

 ward, and terminating at the head. But before one muscular wave is ex- 

 hausted at the head, another has begun to flow, so that two series of undula- 

 tions 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 plen- 

 tiful. 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 Key Biscayne. 



There is considerable confusion regarding the identity of this species. 

 Pfeiffer (in Vol. VI), and Fischer and Crosse (Moll. Mex. et Guat.), consider 

 pontificus as distinct from Kieneri 



Jaw and lingual membrane and genitalia not observed. 



Macroceramus Gossei, Pfeiffer. 



Shell rimate, turrito-cylindrical, obliquely ribbed, white, opaque, with semi- 

 lunar blotches and pellucid, horn-colored spots; spire cylindraceous, apex 

 attenuated and acute; suture crenulated ; whorls 11, convex, the last about 

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

 circular ; peristome briefly expanded, with approaching termini, the columellar 

 expansively reflected. Length, 1 1 mill. ; diameter, 3§ mill. ; aperture, Z\ mill, 

 long, 3\ mill, broad. 



Bulimus Gossei, Pfeiffer, Proc. Zool. Soc, 1845, 137 ; Mon. Hel. 

 Viv., II. 81 ; in Roemer's Texas, 456. — Reeve, etc. — W. G. 

 Binney, Terr. Moll., IV. 135. 

 Cylindrella Hydcana, concisa, etc., see Pfeiffer. 

 Macroceramus Gossei, Pfeiffer, Mon. Hel. Viv., IV. 689. — Tryon, 

 Am. Journ. Conch., III. 302 (1868). — W. G. Binney, L. & Fr.- 

 W. Sh., I. 222 (1869). 

 Var. |3. Somewhat smaller, the spots and blotches more obsolete. 

 A West Indian species, found also in the. Texan Subregion and in the Florida 

 Subregion at Little Sarazota Bay, near Charlotte Harbor, Florida. 

 Jaw and lingual dentition (see p. 384). 



