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BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 46(3)
sembles H. chisosensis Pilsbry, 1927 and H.fullingtoni Cheatum, 1972 by having smooth embryonic whorls. The shells have similar depressed-helicoid shapes as well as similar coloration. Humboldtiana chisosensis differs anatomically by having a wide gap between the dart-glands and dart-sacs (Pilsbry, 1939:400, fig. 272), thereby being more similar to members of the Humboldtiana texana species group (Burch & Thompson, 1957). H. fullingtoni differs from H. presidii by having weaker bands, and by having a wide gap between the dart-sacs and the dart-glands.
Etymology. The name presidii refers to Presidio County, Texas, where the species is found.
The Humboldtiana texana species-group
In this group of species the dart-glands form a ring around the middle vagina and are widely separated from the dart-sacs (Burch & Thompson, 1957).
Humboldtiana balanites n. sp.
Diagnosis. The shell is helicoid in shape, and is nearly as high as wide. The shell wall is thin and fragile. The color pattern is lusterless brown with three poorly defined dark bands and numerous oblique light brown stripes that disrupt the bands. The embryonic whorls are smooth and protruding. The postembryonic whorls have a dense mesh of minute granules that are continuously distributed over the surface from the suture to the base. The lower genitalia is robust. The genital atrium is very abbreviated. The penis is large, bulbous and has a long verge internally. The epiphallus is about 1.5 times the length of the penis. The flagellum is about twice the length of the penis + epiphallus. The lower vagina has four equal-sized dart-sacs. The dart-glands are robust and form a ring widely separated from the dart-sacs. The spermathecal duct is very long, being twice the length of the oviduct-prostate. The spermathecal duct bears a small, slender caecum. The mantle is uniformly light grayish brown.
Shell (Figs. 12-16). This is a moderately sized snail, up to about 33 mm wide with a thin, fragile shell. The shell is helicoid in shape; 0.93 times as high as wide. The periostracum is lusterless. The ground color is dark brown with three nearly black bands. The bands are poorly defined because they are interrupted by numerous oblique light brown stripes and blotches that are aligned with the growth wrinkles. The middle band is the narrowest and the upper band is the widest. The peristome is light purple-brown, and the interior of aperture is brown with a whitish hyaline glaze and banded.
The umbilicus is obliquely perforate (Fig. 15). The mature shell has 4.2 whorls, which regularly increase in size, and then descend to the aperture at the last quarter turn. The upper lip of the peristome inserts on or just below the lower band. The embryonic shell consists of 1.6 smooth protruding whorls (Fig. 16). The first embryonic whorl is 4.4 mm wide perpendicular to initial suture. The postembryonic whorls are coarsely striate and wrinkled along the growth lines, and are sculptured with a dense mesh of low, elongate granules that tend to occur in small clusters that are associated with the lighter transverse stripes and blotches. The granules are continuously distributed over the surface of the shell between the suture and the base. The rotund aperture is 0.79-0.91 times as wide as high. The plane of the aperture lies at an angle of 33 to the shell axis (Fig. 13). The peristome is weakly reflected along the upper and basal lips, hardly so along the outer lip, and forms a short triangular patch over the umbilical area.
Measurements of the holotype and two specimens from 6.6 km E of San Ignacio Arareco are given in Table 2.
Anatomy. The head-foot is uniform gray. The sole is light gray. The mantle collar is light gray as is the area of the mantle overlying the uterus-prostate. The mantle is uniform light grayish brown (Fig. 40) as is typical for the genus Humboldtiana.
Reproductive system (Figs. 17-18). Two specimens were dissected. The holotype is described and illustrated. A specimen from 6.6 km east of San Ignacio Arareco also was examined. Essentially, the latter specimen did not differ from the holotype. Both specimens had spermatophores in the spermatheca, indicating reproductive activity.
The genital atrium is abbreviated and barely distinguishable. The large penis is ovate-bulbous, 11 mm long, and widest above the middle. The penis is thick-walled. The inner wall is lined with thick longitudinal fleshy columns (Fig. 18). Arelatively slender verge extends nearly the length of the cavity. The end of verge is multi-lobed. The penis retractor muscle is slender. It originates on the center of lung about 8 mm posterior to the mantle collar and inserts on the apex of penis where it forms a short sheath around the base of the epiphallus. The epiphallus is slender and is 16 mm long. It is about half again as long as the penis. The epiphallus is reflected to lie along the side of the penis so that the distal end of the vas deferens is appressed along the genital atrium. The epiphallus has four longitudinal folds internally. The flagellum is very long and slender, being almost twice the combined length of the penis + epiphallus, ca. 40 mm long. The flagellum is lined internally with four longi-