Mesogastropoda

Mesogastropoda was for many years a traditional taxonomic group of snails, an order. The order was composed mostly of sea snails, but it also included some land snails and freshwater snails, all of which were prosobranch gastropod mollusks. This order was introduced by J. Thiele in his work from 1921, it and was used for many decades subsequently....
Found on http://en.wikipedia.org/wiki/Mesogastropoda

Mesogastropoda

(from the article `gastropod`) ...modified into a proboscis; nervous system progressively more concentrated; about 30,000 species.Suborder Mesogastropoda (Taenioglossa)Radula ... ...or renopericardial duct; in more-advanced archaeogastropods it opens into the ureter. Separation of the excretory and reproductive ducts occurred ... ......
Found on http://www.britannica.com/eb/a-z/m/76
No exact match found