Emarginula sicula Gray, 1825 Dagger Emarginula
Distribution: Florida, Louisiana, Texas; Cuba; Virgin Islands. Size: 17 mm (3/4 in).
Description: Color whitish-cream; shell cap shaped; base ovate to subcircular; height 1/2 to 2/3 length of shell; shell sculptured with primary ribs radiating from apex and alternating secondary ribs originating away from apex; a third thread is intercalated between the primary and secondary ribs; spiral concentric ribs cross over axial ribs, creating nodules where they intersect and giving a cancellate appearance; shell margin crenulate by the termination of the axial ribs; anal fasciole long, wider at base, produced by closely set arched lamellae; fissure short. Habitat: Hard substrates at depths from 27 to 256 m (89 to 840 ft). Remarks: Using scuba gear and a submersible, Tunnell and Bright found E. sicula at the FGB. See Perez-Farfante (1947). Synonym: E. fissura auct. non Linnaeus, 1758.

Shell reaching a comparatively large size, up to about 16 mm. in length, the height from one half to two thirds the length. Color oyster white or cream. Base ovate or subcircular; young specimens have almost circular bases. Anterior slope convex, posterior slope straight or slightly concave. Apex elevated, close to but a little below the summit, and at the posterior fourth of the shell. Nuclear whorls minute. Anal fasciole conspicuous, provided with elevated arched lamellae winch generally stand out above the margins of the fasciole. These lamellae are less numerous and are farther apart than the concentric cords that cross the shell. Fissure narrow and long, its length being one fourth that of the anterior slope. Sculpture consists of about 20 rather strong ribs radiating from the apex. A short distance from the apex a secondary rib appears between each two of the primary ribs; they are at first rather fine, increasing in diameter until they equal the size of the primary ribs. Finally a thread is intercalated between the primary and the secondary ribs. In some specimens the differentiation of these three types of ribs is not very clear. Numerous concentric threads cross the shell forming small nodules where they intersect the ribs. These threads divide the spaces between the ribs into small, more or less square, pits; this gives to the shell a very fine lattice-like appearance. The sculpture near the apex is very fine, becoming increasingly coarser as it approaches the margin in adult specimens. Margin crenulated by the termination of the ribs. Interior of shell glossy with the outside sculpture showing through in the form of radiating and concentric translucent lines. The primary ribs are marked by shallow grooves. On the interior, the anal fasciole is marked by a grooved callus. Length 12-17 mm; Width 10-12 mm.

Comparison of specimens of E. sicula from the Mediterranean with those from the Western Atlantic, bring us to the same conclusion that Dall reached, that there are no differences which would make possible their separation. We adopt Gray's name E. sicula instead of the better known E. cancellata Philippi, because we agree with many European authors that Gray's description applies to Philippi’s species.
E. sicula differs quite sharply from E. tuberculosa, the Western Atlantic species to which it appears nearest in relationship. In E. sicula the apex is subcentral and the apical whorls minute while in E. tuberculosa the apex is placed near the posterior margin and the whole upper portion of the shell is drawn out and extremely recurved. The lamellae of the anal fasciole in E. sicula are more prominent and more widely spaced than those of E. tuberculosa.

EASTERN ATLANTIC: Channel Islands, probably in the Cantabric Sea, along the coast of Portugal and south to west of Morocco, and in the Mediterranean Sea. WESTERN ATLANTIC: Florida Keys and south all along the West Indies. This species is found in depths of from 8 to 250 fathoms. In the Western Atlantic it has been dredged from 1OO to 150 fathoms and seems to be quite rare.