Comal Siltsnail

The cephalic tentacles are pale, except for black eyespots. Snout is brown, distal lips are pale and foot is pale. Pallial roof has black pigment bands along edges of ctenidium and dorsal edge of genital duct; visceral coil pale except for black pigment on testis. Ctenidium is positioned a little in front of pericardium. There are 24-25 ctenidial filaments, that are broadly triangular with lateral surfaces ridged. Osphradium is narrow, positioned slightly posterior to middle of ctenidium. Radula has about 36 well-formed rows of teeth. Central teeth are about 38 μm wide with convex cutting edge. There are 3-8 lateral cusps. Central cusp are pointed or hoe-shaped, parallel-sided proximally or tapering throughout. There are 1-3 small basal cusps. Basal tongue is U- or V-shaped, about as long as lateral margins. Lateral tooth face is rectangular. Central cusp is pointed or hoe-shaped. There are 2-5 lateral cusps (inner) and 3-7 (outer). Outer wing is broad, flexed, with about 140% length of cutting edge. Basal tongue weakly is developed. Inner and outer marginal teeth both have 14-21 cusps and basally positioned rectangular wing.

Hypobranchial gland is large, overlapping rectum and part of genital duct, thickened alongside kidney. …

The type locality is Comal Creek, near New Braunfels, Comal County, Texas. The original collections of Marstonia comalensis are worn shells having the appearance of drift material. It is possible that Marstonia comalensis became extinct at Comal Springs when this water body temporarily dried in 1964; it is also possible that the shells of this species which have been found at this site were washed downflow from extant populations in the headwaters of the Guadalupe River. Records published by Hershler & Liu (2011) considerably expanded the geographic range of Marstinia comalensis, which lives in springs and fluvial habitats spread among four river basins in south-central Texas. Almost all of these localities are on the Edwards Plateau. Records indicate that Marstonia comalensis was historically distributed in the upper portions of the Brazos River, Colorado River (Texas), Guadalupe River (Texas) and Nueces River basins, south-central Texas. …