Sentence:  The edges of these bones are fringed with hairy fibres, through which the Right Whale strains the water, and in whose intricacies he retains the small fish, when openmouthed he goes through the seas of <WSD>brit</WSD> in feeding time. 
Meaning of the word marked with <WSD> tags:  One of the tiny crustaceans, of the genus "Calanus", that are part of the diet of right whales.