Shell of medium size for the genus height: 9-14 mm, mean: 11, width: 3.4-5.6 mean: 4.3. Solid, subfusiform (H/W: 2.24-3.15 mean: 2.53) . Protoconch multispiral of 2.6 convex whorls, heigth: 480 µm , width: 370 µm : protoconch I of 0.7 whorls, width: 230 µm, covered by thin cancellations, protoconch II with diagonally cancellate sculpture starting after a wide zone under the suture with fine axial threads. Last whorl showing a short keel before the onset of the teleoconch. Protoconch-teleoconch boundary slightly flexuose, opisthocline.
Teleoconch of 6-8 [7]) convex whorls. No microgranules on the surface. Axial sculpture of 16-31 [26] orthocline ribs, and interspaces wider (xl.5) than the ribs. Spiral sculpture above the aperture of 4-9 [8] slightly narrower than the axial ribs. Cancellation rectangular, with low, broad, closely set and hardly detected tubercles at the intersections. Subsutural ramp narrow, with small tubercles in correspondence with the axial ribs tip. Columella simple, slightly sinuous anteriorly, gently angled posteriorly. Outer lip with 10-13 strong inner denticles [12] the most anterior delimiting the siphonal canal, the most posterior delimiting the anal sinus. Siphonal fasciole with 7-8 weakly nodulose cords. Coloration uniformly tawny-reddish, salmon-pinkish in beached specimens. White spiral blotches aside the peristome as broad as 4-5 cordlets. Soft parts. "Body light grey, mottled with purple: pallial tube long, purplish-brown, finely wrinkled; tentacles rather short, cylindrical, light grey; lower portion speckled with white; eyes on long stalks amalgamated with the tentacles, about halfway up the latter; foot narrow; front indented in the middle, with angular comers; hinder part finely pointed; sole white Jeffreys, 1867).

Raphitoma oblonga differs from R. purpurea by its fusiform-pupoid outline (vs. fusiform-acute in R. purpurea), by the more numerous, less elevated and always orthocline axials (vs. mostly opisthocline in R. purpurea), its less marked suture, its tawny-reddish colour (vs. dark brown with withish blotches and a white outer lip in R. purpurea), its shorter siphonal canal.

The Channel Isles, the coast from Saint Malo and St. Lunaire, and Brest (MNHN). There is a not verified record from Salema (Algarve, Portugal) from fishing nets at -60 m (private collection).