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BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 46(3)
Humboldtiana eulaliae Metcalf, 1984.
Humboldtiana torrei Pilsbry, 1935.....
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Literature cited..........................................
INTRODUCTION
The objective of this report is to review the landsnails of the genus Humboldtiana in Chihuahua, and to clarify the status of a single species from west Texas that was thought to be subspecifically related to a Mexican species.
The genus Humboldtiana are a varied group of landsnails found over a large geographic area of western Texas and Mexico. They tend to live in isolated colonies in rocky habitats, many of which are in arid regions. They have received relatively little attention because many of the rocky places in which they occur are difficult to access, and seasonal weather conditions influence the availability of live specimens. These factors, coupled with the historical paucity of systematic malacologists, have yielded an understudied group of organisms.
This report does not pretend to address adequately the taxonomy of Humboldtiana found in the study area. Undoubtedly, only a small fraction of the species of Humboldtiana that live in Chihuahua are known. Chihuahua is the largest state in Mexico. Only a few weeks of field work have been devoted to landsnail surveys there, and only a small fraction of the state has been explored for mollusks.
METHODS AND TERMINOLOGY
Descriptions of new species are based primarily on the holotype. Meristic data as well as significant variations pertaining to other specimens also are included in the description. Morphological features among the paratypes that differ significantly from the holotype are indicated in parenthesis.
The shell height (H) is the distance from the apex to the basal lip parallel to the shell axis. The shell width (W) is the greatest distance across the shell transverse to the shell axis. The aperture height (AH) is measured from the basal lip to the point of attachment of the upper lip. The aperture width (AW) is measured from the edge of the outer lip to the inner edge of the columellar lip transverse to the shell axis. Averages (Avg) and standard deviations (SD) include measurements of the holotype as well as paratypes.
Specimens were relaxed in the field with a weak chloral hydrate solution, fixed for 24 hours in 85% ETOH and then preserved in 75% ETOH. Dissections were
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made in 75 % ETOH with the aid of a Bausch & Lomb 0.7-3.0 sterio-microscope.
In the female reproductive system the dart-sacs and dart-glands may be reduced in size and one or more dart-sacs may be absent in particular species. Two species may have non-homologous but equal numbers of reduced dart-sacs. Thus, for comparative purposes each of the dart-sacs is numbered (ds,, ds2, ds3, ds4) in a clockwise sequence beginning with the dart-sac that faces the atrium and penis {see Fig. 10, 60, 76). The vas deferens ascends along the vagina between ds, and ds4. Abbreviations for other structures in figures of the reproductive anatomy are as follow, agl albumen gland; cae spermathecal caecum; atr genital atrium; db dart-bulb; dgl dart gland; epi epiphallus; fig flagellum; pen penis; pr penis retractor muscle; spt spermatheca; sptd spermathecal duct; utr uterus; vagf. free vagina; vag, lower vagina; vagm middle vagina; vd vas deferens; vrg verge. Internally the penis bears a verge, which is an extension of the epiphallus into the penis chamber. The internal structure of the penis and of the verge are important for discriminating species.
The vagina begins at the union with the penis at the genital atrium and extends upward to the point where the spermathecal duct branches from the uterus. The vagina consists of three segments, the lower vagina (vag,), the middle vagina (vagm) and the free vagina (vagf). The lower vagina is separated from the middle vagina by a ring of dart-sacs. The middle vagina is separated from the free vagina a ring of dart-glands. The relative length of each of the segments is taxonomically significant (Burch & Thompson, 1956).
Species boundaries have become more clearly defined than was apparent in an earlier study (Solem, 1974). Shell characteristics of form, color pattern, embryonic sculpture and postembryonic sculpture constitute valid criteria for species recognition. Anatomical feature, including color patterns and numerous aspects of the reproductive anatomy are useful also for species definitions. Both shell and anatomical features provide bases for showing relationships.
Museum acronyms used in this paper are as follows:
ANSP Academy of Natural Sciences, Philadelphia, PA.
BMNH British Museum (Natural History), London.