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Exi/aSte.froSr the Proceedjag^/the Academy of Natural Sciences of Philadelphia, of papers, 

 ^- .. / By Isaac Lea. 



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i- Description of a New Genus, (TRYFANOSTOMA) of the Family MELANID.E, 



and of forty-five New Species. 



BY ISAAC LEA. 



Read April 15th, 1862. 



Family MELANIDJE. 



Genus Trtpanostoma.* — Testa conica, apertura rhomboidea, inferne sub- 

 canaliculata. Labro expanso. Columella Ijevis} iDfernc contorta. Operculum 

 torneum, ad spiram pertinens. 



The enormous number of species in the genus Melania, has made it very de- 

 sirable to eliminate as many as possible, by founding new genera, when well- 

 characterised groups can be established. With this view, I proposed, in the 

 Proceedings of the Academy in April last, the genus Strephobasis. The genus 

 now proposed, under the name of Trypanosoma, will include all the well-known 

 Jlkanias with an auger-shaped aperture, the type of which may be considered 

 Mr. Say's Melania canaliculala, a common and well-known species from the basin 

 of the Ohio River. 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 increasing the num- 

 ber of genera without the aid of the examination of the soft parts. But there 

 is no validity in this objection, from the fact, that in the present condition of 

 the Science of Malacology, we are becoming acquainted with a vast number of 

 new and interesting forms, without the hope, at present, of seeing the soft 

 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 only 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 Family, but none have made groups of our 

 numerous species by which they can be properly divided. Tliey have mixed 



* Tgwraror, an auger, and s-To^a, a mouth. 



