Cribrilina puncturata (Wood, 1844)
Colonies are encrusting, multiserial, sheet-like, unilamellar and very small, usually containing fewer than 50 zooids. Each autozooid has about 5 distolateral pore chambers visible at growing edges. The ancestrula has a frontal shield with 6-9 costae and lacks associated avicularia.
Autozooids are small, 0.34-0.44 mm long by 0.28-0.37 mm wide, and roughly oval in outline shape. The gymnocyst is extremely narrow. The convex frontal shield is formed by 12-17 tapering costae (including the apertural bar), linked by lateral costal fusions and united at the centre of the frontal shield. There are 3-5 intercostal pores. Lumen pores are lacking. The apertural bar is prominent but narrow and sometimes has a median mucro. The orifice is rounded rectangular, broader than long, with one median, somewhat flattened oral spine in non-ovicellate zooids but no spines in ovicellate zooids. Ovicells are small, globose and have 1-5 small windows in the ectooecium of irregular size, shape and position.
Avicularia are adventitious, paired on either side of the orifice, directed distolaterally or distally, with a short triangular rostrum, raised at its distal end, a rounded proximal end, and an uncalcified pivotal bar.
This Red Crag species of Cribrilina has small autozooids and colonies, enabling its distinction from most other congeneric species found in the East Anglian Crags. The presence of 1-5 small and irregular windows in the ovicell is another important feature that allows it to be recognized. Colonies produced ovicells, indicating female sexual maturity, at a very small size. They are invariably found colonizing the concave, downward-facing surfaces of disarticulated bivalve shells (Bishop 1988).
Pliocene, Red Crag Formation, Walton-on-the-Naze, Essex; Waldringfield, Sutton, Butley, Brightwell, Chillesford, Hollesly, Shottisham and Newbourne, Suffolk (see Bishop 1994, p. 239).