154 



TERRESTRIAL AIR-BREATHING MOLLUSKS. 



PATULA, HALD. 



Fig. 59. 



Animal of Patula solitaria. 



Animal heliciform ; body elongated, semi-cylindrical, tapering to a point 

 posteriorly, convex above, plane beneath ; mantle simple, central, not extend- 

 ing beyond, and accurately fitting to the peristome of the shell, into which 

 the whole animal may retire ; head obtuse ; eyes at the end of long, cylindrical, 

 retractile peduncles ; tentacles short, retractile ; generative orifice on the side 

 of the head, behind the right eye-peduncle; respiratory orifice in the collar, at 

 the angle of the aperture of the shell, anal orifice immediately adjoining ; no 

 caudal mucus pore, no locomotive disk. 



Shell widely umbilicated, depressed, discoidal, turbiuate, rugose, or costu- 

 lately striate ; whorls 4-6, equal or gradually increasing ; aperture lunately 

 rounded ; peristome simple, straight, acute. 



As there appears considerable confusion in regard to the limits of the genus, 

 I think it best to make no reference to any species foreign to North America. 

 Here it ranges over both the Central and Eastern Provinces. 



In none of the American species of this genus have I found a jaw with dis- 

 tinct well-formed ribs as in Helix. In several species, however, such as strigosa 



Fig. 60. 



Fig. 61. 



Jaw of Patula asteriscus (Morse). 



and Cooperi, there are distinct traces of subobsolete ribs near the cutting mar- 

 gin, and still more so in incrustata. In asterwcus there are coarse wrinkles, 

 resembling subobsolete ribs. In perspectiva, striatella, and Idalwensis there are 

 such wrinkles, and also coarse vertical striae. I have not found the striae as 

 oblique as shown in Fig. 61. In solitaria, alternata, and Hemphilli there are no 

 traces of either ribs, wrinkles, or striae. In all these species there is a tendency 

 to a median projection to the cutting edge. This is greatly developed in soli- 

 taria, alternata, Cumberland iana (with perpendicular striaa), and especially in 

 Hemphilli. The last two species have also a much more arcuate jaw than the 

 others. I have not seen the jaw of Horni or pauper. 



