GASTEROPODA OF THE UNITED STATES. 29 



considerably longer, and in the latter presents several 

 large convolutions. In H. intertexta^ H. Ugera, H. gu- 

 laris, and JI. suppressa, it is much shorter. Generally, 

 it is a white, narrow, cylindrical, frequently undulated 

 tube. Sometimes it is distinctly and strongly muscular, 

 as in H. albolahris, H. tridentata, IT. elevata, etc. In 

 ff. fuUginosa its lower part is dilated to the diameter of 

 the penis, and is strongly muscular. In R. albolahris, 

 H. tride7itata, and R. exoleta, at its commencement it 

 presents a dilated and glandular appearance. In IT. 

 solitaria it is much dilated, annulated, and glandular at 

 its termination. In all instances except in II. cellaria 

 and H. alternata, it joins the summit of the penis ; in 

 the two latter it joins the penis at the side, very near 

 the summit. 



The penis varies very much in form and size ; most 

 usually it partakes of a conico-cylindroid form. In 5". 

 sap, H. texasiana, H. inflecta, and II. auriculata, it 

 is very large and long, cylindrical, collapsed, and flaccid. 

 In II. concava it is long, clavate, and bipartite at the 

 summit. In R. altemata, H. perspectiva, and H. solita- 

 ria, it is short, stout, and clavate. In H. albolahris, H. 

 tridentata, H. multilineata, H. arborea, H. dentifera, 

 and H. palliata, it has ;a thick, preputial membrane, 

 originating around its base, and rising upwards so as to 

 envelop it for one or two-thirds of its extent. In H. pro- 

 funda the base of the penis protrudes into a sheath join- 

 ing the cloaca, in the form of a cone with its apex bent 

 upon itself. In H. ligera, H. intertexta, and H. sup- 



