NEW GENERA AND SPECIES OF CENTRAL AMERICAN NAIADES.
BY L. S. FRIERSON.
In 1893 Messrs Crosse and Fischer divided the Mexican Naiades into quite a number of sections, to which they assigned names. Almost simultaneously (in 1900) von Martens and C. T. Simpson, in treating the Central American Naiades, accepted some of these sections of Crosse and Fischer, raising them to generic or subgeneric rank. Because of paucity of material, considerable diversity of opinion concerning the specific identity of several species may be noted in the works of these authors. Furthermore, their work of classification being done independently and from different points of view, the same species was sometimes placed by them in different genera.
Thanks to the arduous labors of A. A. Hinkley, who has again and again enriched our cabinets with material and data from these tropical countries, we are enabled to offer the following suggestions concerning some of the genera of these shells, and also the description of an unpublished species.
Nephronaias. This genus has for its type the Unio plicatulus, Küster, a species identified by von Martens as belonging to the Lampsiline shells, as aztecorum. Mr. Simpson however believed it to be nearly allied to the persulcatus, a markedly Unioid shell. In this the writer follows Mr. Simpson.
The genus Nephronaias as constituted by Mr. Simpson embraces two quite distinct groups, divisible as follows.
Nephronaias (s. s.) embraces plicatulus, persulcatus, melleus, dysoni, ortmanni, ravistellus, etc. Ample material of these two latter species show that they are anatomically very closely allied to Elliptio. There is no sexual difference of shape, and the gill is gravid in its whole length. Nephronaias differs from Elliptio in its sulcated disc, in its beak sculpturing, etc.
Included in Nephronaias by Simpson are, however, shells of a totally different type, such as medellinus, gundlachi, sapotalensis, etc. These latter are sexually dimorphic, smoother, more generally rayed, and the gravid uterus is of Lampsiline type.
The position of the dorsal scars within the beak cavities is different, in the examples of the pseudo Nephronaias seen by the writer. Nephronaias (s. s.) possesses an (accessory?) adductor scar attached to the frontal portion of the cardinal teeth, which is either absent or obsoletely marked in the second assemblage. For this latter group the writer, therefore, proposes to use the generic term of Actinonaias Crosse and Fischer, 1893, type U. sapotalensis Lea. The female of this species has been described by Dr. Ortmann (1912). Actinonaias embraces, besides the type, medellinus, gundlachi, (accepting Simpson’s interpretation of this latter species), and others.
Psoronaias, Crosse and Fischer (1893). This group of remarkable shells, embracing crocodilarum, psoricus, semigranosus, etc., was provisionally treated by Simpson as a group of Elliptio, but their remarkable sculpturing, and the deep beak cavities of some of their species, led him to observe that it was possible that the group should, after all, be placed in Quadrula.
I follow von Martens, in giving generic rank as above to the group. The type is Unio psoricus. To this genus we are enabled to add a species hitherto undescribed, under the name of