Marine gastropods 4 covers all the marine heterobranchs, except the Sacoglossa and Nudibranchia. The popular names for these molluscs include sea hares and sea slugs. In addition, this volume includes a key to all families of shelled marine gastropods found around Britain and Ireland. This leads to additional keys to all British and Irish genera and species. Illustrated species accounts cover diagnostic characters, biology, distribution and range. Heterobranchia is a large subclass of over 26,500 species worldwide, combining two previous subclasses (the Opisthobranchia and the Pulmonata) with a number of other species earlier regarded as caenogastropods. Currently, there are 8,471 marine species within the subclass. The remaining 18,000 or so species are either terrestrial or freshwater animals. But overall only a small subset of the worldwide fauna occurs in British and Irish waters. Marine heterobranchs live in both the intertidal and sublittoral zones. They may burrow in soft substrata, graze Zostera beds or forage on boulder beaches and rocky shores. Although some species forage at the surface, it may be necessary to dig and sieve the sediments. Collection is best at low water on a good spring tide. For the smaller species, a useful technique is to pluck tufts of finer weeds low on the shore, then wash them into a dish. Many of these tiny gastropods may only emerge from material in the lab.
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