OF CONCHOLOGY. IIT 



"Genus Trypanostoma, Lea. 



"Shell conical; aperture rhomboidal, subcanaliculate below 

 Lip expanded. Columella smooth, twisted below. Operculum 

 corneus, commencing spiral. 



" The enormous number of species in the genus Melania has 

 made it very desirable to eliminate as many as possible, by 

 founding new genera, where well characterized groups can be 

 established. AYiih this view I proposed, in the Proceedings of 

 the Academy, in April last, the genus Strephohasis. The genus 

 now proposed under the name of Trypinosloma will include ail 

 the well known Melania with an auger-shape lapeHure, the type 

 of which may be considered to be Mr. Say's Melania canalicu- 

 lata, a very common and well known species from the basin of 

 the Ohio Kiver. It will include a number of large species; 

 indeed, nearly all of the large and ponderous species of the 

 United States. Many new ones will be found in this paper. 

 Objections may be raised against now increasing the number 

 of genera without the aid of the examination of the soft parts. 

 But there is no validity in tliis objection, from the fact that, in 

 the present condition of the science of Malacology, we are be- 

 coming acquainted with a vast number of new and interesting 

 forms, Avithout the hope at present of seeing the organic portion 

 of the animals. These may at some future time, and no doubt 

 will, be examined and carefully described by zoologists who 

 may dwell near the waters where these numerous and highly- 

 developed species reside. Until this takes place, we can onlj 

 group them upon the characters which are presented by their 

 outward hard portions, which are accessible to us now. 



"In proposing this new genus, I am aware that European 

 Zoologists have made many genera and subgenera in this Fam- 

 ily, bat none have made groups of our numerous species by 

 which they can be properly divided. They have mixed them 

 up, with all the time and care they have bestowed upon them, 

 in a manner so as to make great confusion. 



"Mr. Swainson, in his 'Treatise on Malacology,' proposed a 

 subgenus of Melmia under the name of Ceriphasia^ and gives a 

 figure, page 20-1, [C. sulc Ha,) stating it came from Ohio. It is 

 evident, on looking at this figure, that it does not represent any 

 Ohio species, neither in the aperture nor in the revolving ribs. 

 Dr. Gray and Messrs. Adams adopt the genus, and the latter 

 give a figure (pi. 31, fig. 6,) of canaliculU'i, Say, as the type, 

 which I do not think answers to the description or figure of 

 Mr. Swainson. Dr. Gray, in his excellent ' List of the Genera 

 of Recent MoUusca, ' in the Proe. Z(jo1. Soc, expressed a doubt 

 whether his Tel^scopelli may not be the same with Gerip'iasia.^^ 



In iipril, 18(31; Mr. Lea proposed another genus, as follows: 



