120 AMERICAN JOURNAL 



genera tliej seem nearest allied. The operculum of the only 

 one I have seen, is the same as Goniohasis, and the Melanidse 

 generally.'"* 



Dr. James Lewis (Proc. Acad. Nat. Sciences, Dec, 1862, pp. 

 588-90) describes the soft parts of Melania svhnlans and 

 Melania exilis, and remarks in conclusion, that " The following 

 features of the two species above considered may suffice for 

 placing them apart in subgenera : — 



" 1. The presence of a sinus or fold in the sides of the foot 

 and neck of BI. subularis, and its absence in M. exilis. 



"2. The extension of the anastomosins; black lines from the 

 margin of the lateral portions of the foot upwards along the 

 side of the neck in M. suhularis^ and the restriction of these 

 lines to a narrow zone along the lateral portions of the foot of 

 M. exilis. 



"3. A well-defined dark band around the tentacle in M. 

 exilis^ not observable, or at most only faintly indicated in M. 

 subidaris." 



Dr. Lewis endeavors, by these differences, to indicate respec- 

 tively the genera Trypanostoma and Goniohasis of Mr. Lea ; 

 but, unfortunately, the only important character of distinction 

 mentioned by him, is only a sexual difference. 



And now, having cited all that has been done in the classifi- 

 cation of these animals by American and Foreign naturalists, 

 we will first ascertain the sequence of the genera, and then 

 give their names and limitation as we propose to adopt them. 



Swainson commenced with the rpecies having an entire 

 aperture, then he described genera possessing a truncated aper- 

 ture, [Hemisinvs, Jlelanopsis,) and, finally those with a more or 

 less developed channel at the base. 



Dr. Gray's arrangement does not differ essentially ; he adds^ 

 however, Glotella, an intermediate form between the Tnjpa- 

 nostomoid and Goniohasic groups. 



Messrs. x'X.dams commence with the canaliculate species, but 

 not with the highest developed type of that form, — lo. They 

 give the preference to Ceriphasia, Swainson, and next give Pa- 

 chycheilus, which is certainly more of a Goniohasic form, and 

 then give lo. 



Dr. Brot's " Groups" represent nearly the following value 

 and sequence in genera: — Leptoxis^ Trypayiostoma, Goniohasis, 

 Lithasia, Packycheilus, lo, Melanopsis, Gyrotoma, Pirena. 



Mr. Lea, in remarks on his description of Goniohasis, gives 



*Mr. Lea probably did not intend to include his tintinnahulum in Eury- 

 calon, but did so inadvertently. I would add to the description as given 

 above, — shell generally obovate, longitudinally humped or angled ; colu- 

 mella truncate below. The genus may be placed between the Litkaiiis 

 and Goniobases. 



