Castalia stevensi

 (H.B. Baker, 1930)

Castalia stevensi
ANSP 125531 Holotype

Original Description: Tetraplodon stevensi Baker, H.B. 1930:63 in The Mollusca collected by the University of Michigan-Williamson Expedition in Venezuela. VI. Occasional Papers of the Museum of Zoology, University of Michigan. No. 210. 1-81 + 7 plates.

Type Locality: Rio Yuruari (Essequibo River Dr.), Venezuela.

Lectotype: ANSP 125531a. Baker gave measurements for the “Type” but did not specifically designate a holotype.

Paratypes: ANSP 125531 (3); Senck. Mus. 4661 (1).


  • Castalia stevensi (H.B. Baker, 1930)
  • Baker 1930:63; Haas 1931:40; 1966:540.

Castalia orinocensis Morrison, 1943

  • Morrison 1943:14, Type locality: Orinoco River, at Maipures, U.S. Colombia. Holotype: USNM 522000. Paratypes: MCZ 167992 (2 specimens). Haas 1966:540.

Description of C. stevensi: “ANSP 125531: four specimens and two odd valves from the Wheatley Collection labeled “C. crosseanus Hidalgo,” and collected by Dr. Stevens from Rio Yuruari (Essequibo drainage), Venezuela.

Shell (pls. XXXII, XXXIII, figs. B): subrhomboid, subsolid, compressed, with quite prominent and straight posterior ridge. Outlines: anterior and narrowly rounded; posterior arched beyond ligament and truncate; dorsal margin convex (although less so than in most species of genus); ventral slightly so. Beaks quite low and flattened dorsally; not much anterior to center. Exterior: epidermis thick, dark olive-green to brownish; radial castae numerous, almost straight and flattened, tending to break up and anastomose into V-shaped ridges on both anterior and posterior slopes, and becoming weaker or disappearing near ventral margin; growth wrinkles coarse, especially toward ventral edge.

Interior: Nacre pearly to bluish, roughened slightly by the radial plicae; anterior adductor scar impressed; posterior superficial; prismatic zone narrow. Hinge: quite shallow; ligament short and only slightly protuberent externally. Right pseudocardinals: two, almost horizontal lamella; dorsal slender and low; ventral much heavier, higher, and usually broken into two accessory points posteriad. Left pseudocardinal: high and lamellar, usually with one accessory posterior point. Laterals: quite short, usually only one in right valve (one shell has a low accessory ventral ridge) and two in left; ventral side of right tooth and dorsal side of lower left one usually crossed by transverse ridges (absent in type).

This species evidently falls in Simpson’s (1914, Desc. Cat. Naiades, p. 1202) group of T. multisulcatus, although its outline is rather similar to T. schombergianus (Sowerby), which is probably also from the Essequibo drainage. It is nearest crosseanus (Hidalgo) in shape and sculpture, but has flatter, straighter costae, which become irregular at the ends of the shell and scarcely crenulate [on] the ventral margin. T. stevensi is possibly a dwarfed, small stream form of T. schombergianus, but has much sharper, simpler posterior ridge and more regular plicae than those shown by Sowerby (1969, Conch. Icon. XVII, pl. 1, fig. 3).” (Baker, 1930:63-65).

Description of C. orinocensis: “Shell subrhomboid, elliptical, slightly inequalateral, moderately compressed; sculpture of numerous, flat, radiating ridges, crossed by narrow, concentric growth ridges; anterior end evenly rounded. Posterior dorsal slope obliquely truncate; posterior ridge moderate, rounded, ending in a narrowly rounded point a little above the base; dorsal line arched; ventral margin slightly rounded; epidermis olivaceous; laterals long, slightly curved; pseudocardinals irregularly radial, proportionately massive, not linear; nacre white, iridescent behind; anterior adductors, protractor, and retractor cicatrices completely confluent.

The holotype, USNM. No. 522000, was received from Rev. W.H. Fluck, collected on the Orinoco River at Maipures, U.S. Colombia, and measures: Length, 36.6 mm.; height, 24 mm.; diameter, 17.2 mm. The greater degree of inflation, completely confluent anterior muscle scars, and the subradial (massive) pseudocardinals will easily distinguish C. orinocensis from the other members of the group of Castalia multisulcata Hupé.” (Morrison, 1943:14).

Comments: Whether this species is distinct from C. ecarinata Mousson, 1869 or C. schombergiana (Sowerby, 1869) has not yet been determined. The description and figure of the type of C. ecarinata in Haas (1931:40; 89) agrees in many ways with C. stevensi. Need to borrow the type of both species and compare. Haas also lists a specimen of Castalia multisulcatus Hupé, 1857 in the Senckenberg Museum from the Rio Magdalena, Colombia. This should also be looked at.

Specimens Examined: ANSP 125531a (1 Holotype). Yuruari River, a branch of the Orinoco [Essequibo], [Bolivar], Venezuela. Dr. Stevens. ANSP 125531 (3 paratypes). Yuruari River, a branch of the Orinoco [Essequibo], [Bolivar], Venezuela. Dr. Stevens. INHS 14932 (2). Rio Guarico Barbacoas, Aragua, Venezuela. 5 January 1994. K.S. Cummings, C.A. Mayer & G.B. Mottesi. INHS 14804 (35). Caño Masparito, 1 km NW Libertad, Barinas, Venezuela. 14 January 1993. K.S. Cummings & C.A. Mayer. INHS 14910 (10). Caño Hondo, Agua Negra, Barinas, Venezuela. 14 January 1993. K.S. Cummings & C.A. Mayer. INHS 11888 (7). Rio Tinaco, El Baul, Cojedes, Venezuela. 21 December 1990. L.M. Page, P.A. Ceas, M.E. Retzer & A. Barbarino. INHS 14892 (28). Rio Camoruco, between Estero & Campo Alegre, about 10 km NW Libertad Cojedes, Venezuela. 9 January 1993. K.S. Cummings & C.A. Mayer. INHS 14920 (4). Rio Camoruco, 3 km SE Libertad, Cojedes, Venezuela. 9 January 1993. K.S. Cummings & C.A. Mayer. INHS 7661 (1). Rio Mocapra near La Esperanza, Guarico, Venezuela. 23 January 1986. K.S. Cummings, D.A. Carney & D.C. Taphorn. USNM 383185 (?). Caripe River, Caripito [Monagas], Venezuela. E. Martinez. INHS 14890 (22). Caño el Sardinero, 14 km SE Guanare, Portuguesa, Venezuela. 1 January 1993. K.S. Cummings & C.A. Mayer. INHS 14946 (24). Caño El Sardinero, 14 km SE Guanare Portuguesa, Venezuela. 2 January 1994. K.S. Cummings & C.A. Mayer. INHS 14902 (9). Caño Maraca, Portuguesa, Venezuela. 17 January 1993. L.M. Page. INHS 14904 (4). trib. Caño Igues, 20 km SE Guanare on road to Guanarito Portuguesa, Venezuela. 17 January 1993. L.M. Page. INHS 14931 (9). Caño Igues, La Capilla, Portuguesa, Venezuela. 3 January 1994. K.S. Cummings & G.B. Mottesi. INHS 14939 (38). Caño Maraca, on rd. from Guanare to Guanarito at 60 km marker Portuguesa, Venezuela. 30 December 1993. K.S. Cummings & C.A. Mayer.

Localities of species mentioned above:

  • Castalia multisulcatus Hupé, 1857. Type locality: Brazil
    Castalia schombergiana Sowerby, 1869. Type locality: British Guiana
    Castalia crosseana Hidalgo, 1865. Type locality: Imbabura, Ecuador

Other Castalini from the region:

  • Castalia cordata H. and A. Adams, 1857. Type locality: British Guiana
    Castalia retusa Hupé, 1857. Type locality: Guiana
    Castalia quadrata Sowerby, 1867. Type locality: Guiana
    Castalia ecarinata Mousson, 1869. Type locality: Magdalena River, Puerto Nuevo, Columbia

Literature Cited