^26 



On the Anatomical Differences observed in some Species 

 of the Helices and Limaces. By Edwin T. Newton, 

 (ieological Survey. 



(Read December lltb, 1867.) 



ALTHOUfiH in all the pulmonated Gasteropoda the general 

 type of structure remains the same, yet in the different 

 species there arc some important modifications of the various 

 organs. Mr. Binney, in his work on the ' Land Shells and 

 Mollusca of the United States/ has considered very fully the 

 anatomy of many of the Pulmonata, and has given several 

 plates of dissections. He, however, includes only a few of 

 the species found in this country. A paper by Mr. Nun- 

 nely, in the first volume of the ' Leeds Society's Transac- 

 tions,' treats of the comparative anatomy of the Limaces of 

 that district, and some of the facts mentioned by him will be 

 referred to in this paper. 



The differences which we shall have to notice are — in the 

 reproductive organs, where some of the parts become modi- 

 fied or suppressed ; in certain additions to the alimentary 

 canal ; and in the variations which the muscles undergo. 



The ovotestis in the Helices occupies the apex of the shell 

 conjointly with the liver, with which, indeed, it is closely 

 connected. In the Limaces it is perfectly distinct from the 

 liver, and varies in difterent species as to its position with re- 

 gard to other organs in the visceral cavity. In L. maximus 

 it occupies the posterior extremity of the internal cavity ; in 

 L. flavus it is in fi'ont of the first flexure of the intestine ; in 

 L. agrestis it occupies a position beside the intestinal flexure ; 

 and in Avion ater it is situated midway between the posterior 

 extremity of the visceral cavity and the flexure of the in- 

 testine. 



Some of the accessory parts of the reproductive organs 

 found in the Helices are absent from the Limaces. L. maximus 

 and L. flavus do not possess either the dart, the flagellum, or 

 the multifid vesicles j and all the Limaces have a short sper- 

 mathecal duct. L. agrestis has at the internal extremity of 

 the penis three short cfecal tubes, which occupy the position of 

 the flagellum in the Helices (PL IV, fig. 4/')- These ap- 

 pendages of L. agrestis are alluded to both by Mr. Binney 

 and Mr. Nunnely. L. Sower bii possesses the multifid vesi- 

 cles, and in this species they consist of several ovoid masses, 

 connected by very minute threads,, or ducts, with the vagina, 

 near its junction with tlie duct of the spcrmatheca (fig. 2g). 

 The spcrmatheca is proportionately large in L. Soiverbii, and 



