A MANUAL OF AMERICAN LAND SHELLS. 43 



the visceral cavity, just posterior to the position of the puhnonary cav- 

 ity. The penis sac often has a flagellate appendage containing the 

 curious organ known as the capreolus. The above are the male organs 

 of the compound system. 



The female organs consist of the ovary, a linguiform body, some- 

 times lobulated, at the posterior end of the genital system. The oviduct 

 is a long sac-like body, usually greatly convoluted in its course. It 

 decreases in breadth at its anterior end, and gradually merges into the 

 vagina, a long tube-like body of uniform size to the common external 

 orifice ; into its lower end, called by Dr. Leidy the cloaca, enters the 

 penis sac, and above this enters also the duct of the genital bladder. 

 This last organ, as well as the bladder itself, varies greatly in size and 

 length, and forms an excellent specific character. 



The above is the simplest form of the genital system, all these organs 

 being absolutely necessary. It is often much more complicated by 

 having an accessory, very much lengthened duct to the duct of the 

 genital bladder, by various forms of vaginal prostate glands often with 

 complicated accessories ; with one or more dart sacs entering into the 

 vagina, containing a dart of various shape. The penis sac also some- 

 times has curious and varied accessories. All these organs may be 

 found in some species of any given genus, while other species may have 

 only the organs necessary to the genital system.* I am induced, there- 

 fore, to consider the details of the generative system to be only a spe- 

 cific character. As a generic character we can rely only on the position 

 of the external orifice of the system, and on the position of the testicle 

 as well as the form of the coeca which compose it. Thus Glandina, 

 Zonites, and Ariolimax have the external orifice under the mantle, while 

 usually it is found behind the right eye-peduncle. Again, Limax, Ario- 

 limax, Prophysaon, HempJiiUiay Arion, Glandina, and Succinea have the 

 testicle free, and formed of a ciniform cceca, while in the genera of dis- 

 integrated Helix and others it is composed of fasciculi of elongated 

 cceca commingled with the substance of the upper lobe of the liver. 



In comparison of the descriptions of genitalia in this work with those 

 given by foreign authors, it must be remembered that the terms ovary, 

 testicle, &c., are not applied to the same organ. 



In Vols. I and V of Terr. Moll. U. S. will be found figures of the gen- 

 ital system of many of our species. I have in this volume repeated the 



*For instance, in Arionta we find the necessary organs only iu Townsendiana , but 

 in Nickliniana and other species a great variety of accessory complications. 



