Bothrium

Bothria (from Greek bothrion = small pit, diminutive of bothros = pit, trench) are elongate, dorsal or ventral longitudinal grooves on the scolex of cestoda. They have weak muscles but are capable of some sucking action. Bothria occur as a single or two pair and are typical of the order Pseudophyllidea (e.g., Diphyllobothrium). ^{[1] [2]}

References

1. Richard C. Brusca, Gary J. Brusca. Invertebrates. Sinauer Associates; 2 edition. 2003
2. Jones MK, Beveridge I, Campbell RA, Palm HW. Terminology of the sucker-like organs of the scolex of trypanorhynch cestodes. Systematic Parasitology 59: 121–126, 2004.