Pulmonifera of 3Iaine. 3 



and family distinctions ; basing these groups on the differences or 

 resemblances seen in the structural peculiarities of all the principal 

 parts of the animal, such as the characters of the lingual membrane, 

 form of the buccal j^late, contour of the entire animal, and every- 

 thing I could lay hold of in my limited sphere of observation to 

 guide me in this arrangement. I have been continually on my 

 guard not to lean too much on a single feature, but to consider 

 imi^artially all parts together. As yet, this can only be done 

 imperfectly, and it will require long and pains-taking research 

 before the end is attained. In fact, the interpretation of the natural 

 subdivisions which I believe to exist in these animals, demands 

 a deeper and more philosophical mode of study, a complete 

 embryological history of all the si^ecies, an exhaustive histology 

 and a thorough anatomy of the soft parts; and then whatever 

 may be revealed by such work, will, I believe, be as characteris- 

 tically stamped on the shell as on the habits and economy of the 

 animal. Finally, the definitions of Professor Agassiz regarding 

 genera, namely, details of structure; and of families, namely, 

 form, will be the long hidden keys to unlock and make plain the 

 relations of this group. 



In a paper now in preparation, on the classification of the 

 Pulmonifera, I shall point out fully my reasons for the following 

 arrangement. Considerations regarding all the forms of this 

 order, and not merely those confined to the State, govern the 

 groupings given in this table. 



In the Helicida?, (as restricted here to those animals which 

 sustain a globose or planospiral shell) we have noticed thus far 

 three principal types of lingual dentition. 



(1.) In those larger forms of Helices which we include under 

 the sub-family Ilelicinee, we have in the lingual membrane about 

 one hundred rows of plates, with about seventy-five plates in a 

 row. The laterals and uncini are scarcely distinguishable one 

 from the other ; in fact they may be said to blend together. The 

 centrals and laterals are unidentate and similar in form; ths 

 uncini either unidentate, bidentate, or irregularly notched. The 

 Ijuccal plate is solid, arcuate, its frontal portion strongly marked 

 with longitudinal ribs which crenulate the cutting edge. 



