Mexistrophia Thompson, 2011

Original Description

Mexistrophia new genus

Type Species: Mexistrophia reticulata new species.

 

Description:  Shell small, 10-13 mm length. Shell pupiform, with a low dome-shaped apex. Protoconch whorls smooth and do not conspicuously rise above fol­lowing whorl. Peristome thickened, but only slightly so, not reflected, incomplete across parietal wall. Outer lip and columellar lip connected by thin parietal callus. Outer surface sculptured with fine axial thread -riblets. Internal axis broad and hollow in upper whorls of dome-like apex, then narrowing and becoming narrowly per­forate or solid in last two or three whorls. Internal barrier of lamellae or denticles lacking at all growth stages (in contrast with Cerion.)

 

Anatomy: General anatomical states typically Cerionidae.  Short foot lacking a suprapedal groove. Plain lung, with unbranched pulmonary vein. Kidney short, with very short ureter near the end. Secondary ureter absent.

 

Reproductive system typically cerionid.  Genital atrium moderately long and capacious, Epiphallus poorly differ­entiated from vas deferens.  Epiphallus + vas deferens form very long loop that extends alongside oviduct-­prostate. Penis consists of two parts. Epiphallus entering middle of penis.Penis ending in blind diverticulum distal to epiphallus, Penis retractor muscle inserts on apex of diverticulum.  Right ocular retractor muscle passes mesad to genitalia and attaches to right pedal retractor muscle. Spermathecal duct very long, with very long appendix, or lacking an appendix. Spermathecal duct unites with free oviduct to form distinct vagina.  Free oviduct stout and slightly longer than vagina. Stout vaginal retractor muscle originates on right ocular retractor muscle and inserts on vagina (Figures 24-25).

Radula of Mexistrophia is typical Cerionidae with nearly flat horizontal tooth rows that do not curve upward near margins. Central tooth  tricuspid. Lateral and marginal teeth bicuspid with large mesocone and small ectocone. Mesocone of marginal teeth long, extending beyond base of tooth. Laterals and marginals lacking entocones

 

Habitat and Distribution: Mexisirophia are ground­ dwelling snails that are found in eastern Mexico in cool temperate coniferous forests at high elevations.

 

Etymology:  Mexisirophia (f.). The genus name is taken from Mexi-, Mexico , and strophia, Gr. stroje, a turning point, such as an axis.  Strophia Albers, 1850 is an earlier generic name that was widely used for Cerion (not Strophia Meigen, 1832, Lepidoptera).

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