|
|
|
|
|
|
Conus symmetricus (Sowerby I, 1850)
Description
Shell turbinate, short and broad, spire short, spirally striate; body whorl sharply carinate at the shoulder, ornamented with granulose spiral threads alternating with one or two finer smooth spirals; the canal is slightly produced and a trifle reflexed.
Length of shell 29, greatest width 18 mm.
Locality. — (Exp'd '16) Zone E, Rio Gurabo at Los Quemados.
Conus symmetricus, which is a common species, especially in the Gurabo Fm.(Pliocene), has a very distinctive shell shape that is not easily confused with co-occurring species. Its relationship to extant species is not clear. Petuch stated that C. tristensis Petuch, 1987 “probably represents the last living member of the C. symmetricus-dominguensis species complex” (4).
Kohn considered C. tristensis a synonym, albeit somewhat tentatively, of C. cancellatus Hwass in Bruguière, 1792, which was assigned to the subgenus Dauciconus by Puillandre et al. While many specimens of C. symmetricus have an overall shell shape that is somewhat similar to that of the holotype of C. tristensis, specimens of C. symmetricus always have beaded ribs on the last whorl, which were not reported by Kohn in his recent description of C. cancellatus. Additionally, shells of C. symmetricus are widest below the shoulder, but specimens of C. cancellatus are usually widest at the shoulder (4).
Finally, coloration patterns similar to those described above for C. symmetricus are not present in any known specimens of C. cancellatus, which are often—though not always — unpigmented (4).
|
|
|
|
|
|
Conus symmetricus var. domingensis (Sowerby I, 1850)
Gabb and Guppy united Sowerby's C. domingensis with C. symmetricus. A specimen of the former species loaned by Dr. Dall from the National Museum shows it to be a flat-topped, broader shouldered mutation of C. symmetricus. This elegantly sculptured Cone is very common in Santo Domingo and is found at Bowden and Gatun.
Localities. — (Exp'd '16) Zones A, B, C, D, E, F, Rio Gurabo at Los Ouemados; Bluff 1, Cercado de Mao.
|
|
|
|
|
|
mm. 28,3 x 20,5
Conus symmetricus var. domingensis is a broader shouldered mutation of C. symmetricus |
Conus symmetricus var. semiobsoletus (Sowerby I, 1850)
Shell resembling C. symmetricus in form but larger and with the granular spirals obsolete on the upper half of the body whorl.
Length 39, greatest width 24 mm.
The specimens were collected by Professor Gabb in Santo Domingo.
|
|
|
|
|
|
|
mm. 28,3 x 20,5
|
Bibliografia Consultata
