Taxonomic Atlas of the Benthic Fauna of the Santa Maria Basin and Western Santa Barbara Channel Volume 9 The Mollusca Part 2: The Gastropoda

by James H. McLean and Terrence M. Gosliner. Edited by Paul H. Scott, James A. Blake and Andrew L. Lissner. Published by The Santa Barbara Museum of Natural History, 1996. 49 b/w plates. 228 + vi pp. paper bound. 8.5" X 11"
The mollusks of the west coast of North America are a varied and interesting fauna. The coastal waters of the eastern Pacific and the life that inhabits them are all strongly tempered by thermal barriers and cold currents from the north. Equally influential are the effects of species from the Indo-Pacific that flow into the region along both northern and southern routes. The central portion of this coast, extending from Point Conception north of Santa Barbara all the way down into Mexico along the Baja California coast, is known as the Californian Province. (North of Point Conception, all the way to S. Alaska, the molluscan fauna is recognized as the Oregonian Province. Running from the inner Baja coastlines of the Sea of Cortez down to Ecuador is the Panamic Province.)

In 1969 (rev. 1978) James McLean (Natural History Museum, Los Angeles) published Shells of Southern California, treating the northern section of the Californian Province, down to about 70'. In it he covered the mollusks of the habitats most accessible to man, the intertidal and sublittoral areas and the fertile kelp beds. Now Dr. McLean, and Terrence M. Gosliner of the California Academy of Sciences, return to this place where north meets south, Southern California, as the focus for a new identification manual. Addressing the same geographical area as McLean's 1969 guide, this new work has as its objective the benthic mollusks, those occurring offshore, out of easy diving depth down to about 500'. Here there is a low temperature variation -- 50° to 70° -- contributing to a very rich fauna, and one less common in collections than shells of the inshore areas. Intended primarily as an identification manual, the Taxonomic Atlas is less a picture book than many recently published works; instead it is a scholarly workhorse more along the lines of E. A. Kay's Hawaiian Marine Shells, with new species, revisions of genera, species lists, careful outlining of lab methods and conventions, as well as keys, glossaries, maps, collecting stations and extensive bibliographies. There is some species overlap with McLean's earlier work.

The guide is convenient structurally, being organized into two sections, or chapters. Dr. McLean has authored the first, that on the Prosobranchia (used in the traditional sense), and a continuation of the work he began in 1969. Dr. Gosliner authors the second chapter, "The Opisthobranchia." Each stands alone, with separate introductory and supplementary sections. All species are illustrated in crisp black and white photos, and drawings and SEM photos as well in the Opisthobranch section.

The introductory material to both chapters is extremely helpful for the amateur, to give him a good grasp on the higher level systematic and taxonomic changes that have occurred in the recent past, at least for the groups covered, and to explain them. The guide itself is an important addition to the literature. It pictures and discusses 126 species in the Prosobranch section, 7 of them new to science, and 29 species of Opisthobranchs, 7 of them undescribed. Many of the species are here pictured for the first time in a popularly available work.

The Prosobranch fauna covered is an interesting one, devoid of the usual cones, cowries, murexes and volutes. But there are a trivia, and two simnias. Lots of little eulimids. A host of Trophoninae, those coldwater murex so dear to collectors, inhabit the region, including four new to science. There's also a new Trophon genus, Scabrotrophon, erected here for those species having their dominant early sculpture spiral, and with scabrous spiral cords on mature specimens. The pure white S. clarki ns., strikingly beautiful with its fluting and ruffles and imbrications, is also satisfyingly large (43.4mm holotype)and rare (2). Another new species, the minute Megalomphalus schmiederi, has both the plenitude and elegance of ribbing of a Harpa costata, all in 2.5mm.

The Opisthobranch chapter is a useful and interesting one, and its introduction is a good jumping off point for an avid beginner in the group. Gosliner's introduction is excellent for this purpose. There are almost 5,000 species, almost all marine, and these waters are rich with them. The species from deeper water are not well known, with most of the recorded taxa being shelled species described from dead shells. Both the shelled and the shell-less and internal-shelled species are covered here. Seven are undescribed species, and two genera were previously known only from the Atlantic.

This guide should be part of the equipment of any serious sheller. It, with McLean's earlier book, provides a good picture of the region's fauna. But should one's interest extend farther north, there's good news about a previously scantily covered fauna: Dr. McLean has, in the works, an illustrated manual of the entire Californian and Oregonian Provinces, covering 1,000 species.


Published in the June 1997 issue of American Conchologist.