Page:Land Mollusca of North America (north of Mexico) Vol. I Part 1 277-end.pdf/135

LAND MOLLUSCA 411 Helices without dart apparatus; penis continued in an epiphallus and a flagellum (the latter sometimes vestigeal or wanting); spermathecal duct not branched.

This group of helices has been accepted by systematists in the sense of the original definition, though it has been enlarged by the inclusion of genera unknown or not dissected at the time it was instituted, and various family names have been used for it. In 1895 these snails were termed Epiphallogona, to separate them from the preceding families, which collectively form the superfamily group Belogona.

While the Epiphallogona apparently form a natural group, several subordinate structural types are included, and further investigation is required to show whether all of its genera are to be retained in the single family Camaenidae, or divided among several families. In case further division is made, our genera shall form the families Ammonitellidae and Oreohelicidae. Pending further study of Asiatic and East Indian epiphallogonous helices our west American representatives are here left in the Camaenidae as subfamilies.

It does not appear practicable, at present, to define this group of helices briefly, in a way to exclude presumably belogonous helices which have lost the dart apparatus. However, the shells are rather different; they do not have the five-banded pattern, or the single shoulder band, common in belogonous helices, but plain and many-banded shells occur in both groups. In many genera the shells are large and solid.

Helices of this stock seem to have had an early radiation in Mesozoic time, reaching Australia, perhaps with the marsupials, and spreading to Europe, where they are known in the Eocene by Dentellocaracolus and other genera. The presence of Oreohelix in the Upper Cretaceous of Alberta is evidence of an early advent in America.

Although tropical American helices such as Pleurodonte, Polydontes and Zachrysia have been recognized since 1895 as part of the epiphallogonous series, the relation of our Ammonitellid and Oreohelicid snails to this group has been overlooked up to this time. The genera have been scattered among Polygyridae and belogonous helices.

The widely deployed West Indian and South American genus Pleurodonte is represented in the Lower Miocene Silex Beds of Tampa Bay, Florida, by one or two species described (1890) as Helix, but later referred to Pleurodonte (Dall, 1915, U. S. Nat. Mus. Bull., 90: 23-4). They do not seem directly referable to any of the West Indian subgenera, and the subgenus Pleurodontites, with the type P. haruspica (Dall), is here proposed for them. The species are P. haruspica (Dall), and with some doubt, P. diespiter (Dall). "Pleurodonte" eohippina Cockerell, 1915, Bull. Amer. Mus. Nat. Hist., 34: 119), from the Sand Coulée Eocene, Wyoming, does Generated on 2012-11-10 02:35 GMT / http://hdl.handle.net/2027/uc1.31822013176466 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google