This study reports the tirst record of 17 species of gastropods collected on the continental shelf off Jalisco and Colima, Mexico, in August 1988. Samples were taken with a Van Veen grab and net trawls at depths between 40 and 98 m. Substrates consisted of medium sand, sandy silt and silty clay. Previous range distributions of eight species (Cosmiconcha rehderi, Cyclostremiscus planospira, Knefastia howelli, Kurtzia elenensis, Leptadrillia fìrmichorda, Mirachelus galapagensis, Nassarina perata and Phos fusoides) included localities between Guerrero, Mexico, and Ecuador. Previous records of the other nine species (Parvanachis albodonosa, Atilliosa carmen, Knefastia walkeri, Kylix paziana, Mitrella dorma, M. xenia, Strombina solidula, Sulcoretusa paziana and Turritela anactor) included localities in the Gulf of California, Sinaloa and Nayarit, Mexico. These species belong to two subclasses, four orders, eight families and tifteen genera of gastropods. Information on abundarme, distribution with respect to depth and type of substratum and range distribution is also provided

This study examines the distribution and abundance with respect to depth and type of substratum of 86 gastropod species collected from the Pacific continental shelf off Jalisco and Colima, Mexico, in August 1988. Sampling was performed with a trawl net at 22 stations, at depths of 18 to 112 m. A total of 582 individuals pertaining to 42 genera, 25 families, 4 orders and 3 subclasses of gastropods were collected. Abundance of gastropods was similar between 18 and 83 m, but the number of live individuals decreased between 41 and 60 m. Deep (61-83 m) stations registered the lowest diversity; however, the number of species collected alive decreased with depth. No gastropods were collected at stations deeper than 83 m. The number of individuals and species also varied with the type of substratum. Greater heterogeneity of the sediments was found at the shallower stations (18860 m) with medium sand, sandy silt and silty clay substrata. The greatest number of species were collected at stations with sandy silt and medium sand substrata. Total abundance was notably smaller in medium sand, while the abundance of live gastropods was higher in silty clay substratum. The seven most abundant species represented 5 1.2% of all of the individuals. Most of these species are of commercial interest, in particular those of the genera Fusinus, Hexaplex, Ficus, Harpa, Cantharus and Bursa.

Recibido en enero de 2002; aceptado en diciembre de 2002 ResumenEn la presente investigación se analiza la distribución y abundancia de 15 especies de moluscos escafópodos recolectados en la plataforma continental de los estados de Jalisco y Colima, México, en agosto de 1988. Los escafópodos fueron recolectados mediante una draga geológica tipo Van Veen en ocho estaciones de muestreo, a profundidades entre 23 y 75 metros en sustratos limo-arcilloso, limo con arena fina y arena media. Se identificó un total de 222 individuos pertenecientes a cuatro géneros y dos familias. La mayor abundancia se registró entre los 72 y 75 metros, en fondos limo-arcillosos. Ocho especies fueron las más abundantes, representando el 86% del total de individuos: Fustiaria splendida (21.3%), Dentalium neohexagonum (16.7%), Cadulus perpusillus (11.3%), C. fusiformis (10.4%), D. sp.2 (8.6%), C. albicomatus (5.9%), F. brevicornu (5.9%) y D. sp.1 (5.9%). La aplicación del análisis de ordenación de Bray-Curtis permitió que se definieran tres grupos que responden a la distribución y abundancia de las especies, y a la influencia de factores ambientales, entre los que destacan, la salinidad y la profundidad.Palabras clave: escafópodos, moluscos, plataforma continental, Jalisco, Colima. AbstractThe distribution and abundance of 15 scaphopod species collected in the continental shelf off Jalisco and Colima, Mexico, in August 1988 were analyzed. Scapohods were collected with a geological Van Veen dredge in eight sampling stations at depths from 23 to 75 m in medium sand, sandy silt and silty clay substrata. A total of 222 individuals belonging to four genera and two families were recognized. The highest abundance was recorded between 72 and 75 m in silty clay substratum. The eight most abundant species represented 86% of all individuals: Fustiaria splendida (21.3%), Dentalium neohexagonum (16.7%), Cadulus perpusillus (11.3%), C. fusiformis (10.4%), D. sp.2 (8.6%), C. albicomatus (5.9%), F. brevicornu (5.9%) and D. sp.1 (5.9%). The Bray-Curtis ordination analysis allowed the recognition of three groups responding to the distribution and abundance of species, and to the influence of environmental factors of which salinity and depth were the most important in this analysis.