STUDIES IN MARINE ECOLOGY. 1 69 



So far as possible, identification was done in the field. Doubt- 

 ful specimens were referred from one instructor to another. 

 Specimens new to the locality or difficult to identify were brought 

 into the laboratory for further study. With the exception of 

 the arthropods, few of the specimens have been referred to 

 experts although we have gradually accumulated a type collection 

 of animals found. The identification of animals has been made 

 on the conservative basis that when doubt existed, the specimen 

 was referred to the more common species. Wild identifications 

 have been eliminated as far as possible, even to the extent of 

 throwing out the entire reports of inexperienced instructors. 



In spite of this care, mistaken identifications have probably 

 been turned in and accepted. The list here given is substantially 

 correct since the animals have either been reported by qualified 

 collectors or placed on the list from demonstrated specimens* 

 The imperfections lie largely in failing to distinguish closely 

 related species and in possible errors in distribution records. 



II. 



The collections upon which this series of reports are based 

 have been made largely in the littoral zone as defined by Edward 

 Forbes ; that is, between high water and a depth of two fathoms. 

 This is not the littoral zone of modern zoologists, but the term 

 has been used with so great a variety of meanings that the 

 extent of the study can be more easily and definitely located as 

 being in the intertidal and ad- or sub-tidal regions. 1 



The intertidal zone is much restricted in the Woods Hole 

 region on account of the slight rise and fall of the tides. The 



1 Murray and Hjort use the term "littoral zone" to include the region near the 

 shore down to a depth of 30 or 40 meters: "almost as far as there are sea-weeds." 

 It is frequently used as by Petersen to include the entire continental shelf. The 

 botanists tend to be more exact. Kjellman limits the term to the region between 

 extreme low and extreme high tide. Davis regards the littoral zone as extending 

 from about mean low water to the highest point at which algae can grow. Flattely 

 and Walton ('22) follow Cotton ('12) and define the littoral region as extending 

 from the level of highest marine vegetation, to low water at neap tide. 



I prefer to use littoral in its original meaning of "pertaining to the shore"; 

 intertidal or tidal zone adequately and exactly describes the region between the 

 tide lines, and sub-tidal or adtidal are exact terms, if not the most correct etymolo- 

 gically, for the region below low tide. The question is discussed in the Biological 

 Survey, p. 179. 

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