C. tubercularis has deep siphonal notch, resembling siphonal canal of Neogastropoda, inclined to left at base of columella (1). Notch interrupts lip of aperture and is visible in abapertural view (2).
B. reticulatum has short, shallow, inhalent anterior sinus inclined to left at base of columella (3). Notch does not interrupt lip of aperture and is not visible in abapertural view (4).
13 Bittium reticulatum h. 6.2mm (right) compared with Cerithiopsis tubercularis h. 4.7mm (left). Llŷn Peninsula and Menai Strait, North Wales.
