"Sensu stricto" means "in the strict sense". "Sensu lato" means "in the
broad sense".
For example, Murex pecten is a Murex, sensu stricto. It is in the actual
genus Murex. Murex pomum is a murex, sensu lato. It is actually a
Phyllonotus, mut it is a murex in the broad sense of ther word.