Tryonia hertleini (Drake, 1956)
Lyrodes hertleini Drake, 1956:44-46, pi. 15 [type locality, springs at Las Palomas,
Chihuahua, Mexico].
Fontelicella Aerf/em/.-Taylor, 1975:95 [reassignment].
Tryonia hertleini.—Hershler and Thompson, 1992:110 [reassignment].
DIAGNOSIS.—Shell medium-sized, conical. Penial ornament
of 2 distal and 1 massive basal papillae on inner edge.
DESCRIPTION.—Shell (Figures 4D, 23D) 2.5-3.2 mm tall.
Whorls, 4.75-5.5, medium convexity; teleoconch sculptured
with a few spiral lines. Aperture ovate, lip complete, thin, adnate;
shell imperforate or narrowly umbilicate. Operculum
ovate, inner side smooth. Ctenidial filaments about 33, pleated.
Stomach without posterior caecum. Radula with about 36 rows
of teeth, the posteriormost 10 weakly developed; length/width
of ribbon 460%. Dorsal edge of central radular teeth weakly indented,
basal tongue broadly V-shaped, central cusps narrowly
pointed, lateral cusps 4 or 5, basal cusps 2. Lateral teeth with 2
cusps on inner side and 4 or 5 cusps on outer side; outer wing
strongly flexed, length 260% of tooth-face width. Inner marginal
teeth with 15-17 cusps, outer marginal teeth with 26-32
cusps.
Prostate gland large, thick, subglobose, pallial section 33%
of total length. Distal penis without pigment, well-developed
swelling along inner edge, penial duct undulating (Figure 26D).
Oviduct loop anterior-oblique, pigmented. Brood-pouch opening
terminal, slightly thickened; brooded embryos about 18,
forming 2 rows in posteriorly folded section. Albumen gland
on right side of bursa copulatrix. Bursa copulatrix large for genus,
ovate; seminal receptacle much smaller than bursa copulatrix,
ovate. Sperm-duct opening to distal portion of bursal duct.
Sperm-tube opening to posterior 33% of pallial cavity.
DISTRIBUTION.—Las Palomas, interior drainage of northeast
Mexico. This species may be extinct because its only known
locality dried more than 25 years ago (Landye in Hershler,
1994).
REMARKS.—Tryonia hertleini is distinguished from other
congeners by the massive basal papilla on the inner side of the
penis (Figure 26D). The highly elongate outer wing of the lateral
radular teeth of this species also is unique in the genus.
The holotype of this species has a broken aperture, so a
paratype was figured instead (Figure 23D). Note that the
UMMZ alcohol-preserved material studied was collected during
an ichthyological survey and was not relaxed.
MATERIAL EXAMINED. MEXICO. Chihuahua: springs at Las
Palomas, CAS 64918 (holotype), CAS 64919 (paratypes),
USNM 600498 (paratypes); spring-fed pond 3.6 miles [5.8 km]
south of Las Palomas, UMMZ uncataloged.
Hershler, R. (2001)
Systematics of the North and Central American aquatic snail genus Tryonia (Rissooidea: Hydrobiidae). Smithsonian Contributions to Zoology, 612, 1–53.
