File:American malacological bulletin (1988) (18157382441).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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88 AMER. MALAC. BULL. 6(1) (1988)
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Figs. 30-33. Acanthochitona astngera (Reeve, 1847), type specimens; Barbados. Fig. 30. Paralectotype, 22.0 mm; BM(NH) 19809/1. Fig. 31. Lectotype, 19.0 mm; BM(NH) 19809/4. Figs. 32, 33. Paralectotypes, 19.5, 22.0 mm; BM(NH) 19809/3, 2. Three of four specimens encrusted to varying degrees by cor- alline algae, although some valves have been cleaned. Valves of smallest specimen in excellent condition. Girdle brown, encroaching over anterolateral areas of valves so that intermediate valves are shield-shaped. Valve color varying from brown with white maculations laterally to dark blue-green, approaching black; where tegmentum damaged, underlying shell blue-green. Tegmentum covered with small pustules, drop-shaped near jugum, more ovate near center. Pustules of valve i small, ovate near apex, larger, drop- shaped near margins. Jugum of intermediate valves slender, with nearly smooth surface rendered finely striate by linear arrangement of fine pits near margins, pits exposed across entire jugal width near beaks; subsurface striations visible through smooth jugum surface in remaining areas. Valve viii with drop-shaped to ovate pustules as on other valves; mucro relatively low, posterior of center; jugum smooth, but with longitudinal striae visible beneath transparent surface. Spicules of anterior and sutural girdle tufts extremely dense, white, straight, very slender; numerous very small spicules on dorsum of girdle; spicules at girdle margin stout, long, approximately Vz length of those in tufts, overlying shorter, sharp-tipped spicules, both types glassy, white; under- side of girdle with very fine, short spicules protruding through. Fragments of foraminifera and carbonate particles trapped among girdle spicules. SUPPLEMENTAL DESCRIPTION: Largest specimen (FSBC I 32528) 25.2 mm long, 15.0 mm wide; valves occupying about 30% total specimen width (Fig. 34). Valves dark blue-green to black, usually with white, stripe-like maculations on valves ii and v, less commonly on other valves. Girdle blue-green, brown, or black, virtually obscured by expanded tufts of long, slender spicules. Valve i semilunate (Fig. 35), wider than long, posterior margin straight, with anterior insertion plate bearing 5 slits; tegmentum occupying approximately 70% of valve length. In- termediate valves ii-vii beaked posteriorly, with smooth jugum widening anteriorly (Figs. 36, 37); tegmentum pentagonal, as long as wide in all but smallest specimens, with straight to slightly convex anterolateral margins; sutural laminae large, broad, curving anteromedially from posterolateral corners of tegmentum, with broadly to acutely rounded tips separated by broad sinus; single narrow slits along lateral margins. Valve viii tegmentum trigonal (Figs. 38-40), widest anteriorly, with anterior margin straight at broad sinus; mucro elevated, posterior of center; sutural laminae very well-developed, broad, slightly or markedly sinuous along margins; two slits in posterior insertion plate distinct, varying in width and depth. Valve viii often misshapen, asymmetrical or missing features (Figs. 39, 40). Pustules of tegmentum ovate to drop-shaped (Fig. 41), shallowly cupped, 80-90 /tm long, constricted adapically, with single, large, macresthete, 1-3 micresthetes at juncture of apex and tegmental plain. Girdle upper surface dominated by 18 anterior and sutural tufts each comprised of more than 100 white to light amber, long (to 4 mm), slightly curved, slender, sharp-tipped spicules; background spicules of dorsal surface short (100 /iin), straight, sharp-tipped, blue, brown, or black; marginal spicules white, approximately 500 /*m long, straight, slender, sharp-tipped; underside covered with fine (80 ^m), sharp- tipped spicules directed toward periphery. DISCUSSION: The dark blue-green valves, densely packed, long, slender, sharp-tipped spicules of anterior and sutural girdle tufts, and white maculations on the blue-green tegmen- tum, often only on valves ii and v, leave no doubt that specimens reported here as Acanthochitona astrigera are con- specific with those described by Reeve. Bullock's 23.5 mm specimen from Barbados is identical in all respects with Reeve's syntypes. Reeve's smallest specimen, illustrated in Fig. 31, is designated herein as lectotype. E. A. Smith (1890) initiated the confusion between Acanthochitona astrigera and A. spiculosa with the statement: "(Reeve's) figure (47) of the detail of sculpture of C. spiculosa, Reeve, which I believe to be the same species (as C. astrigera), gives quite as good an idea of the ornamentation (of astrigera) as (Reeve's) figure 109." Pilsbry's (1893) diagnostic comments indicate that he correctly recognized

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