Répartition quantitative et bathymétrique des ptéropodes thécosomes récoltés en méditerranée occidentale au nord du 40" parallèle, remarques morphologiques sur certaines espèces

This study is based on the observation of an abundant material collected over a number of oceanographic cruises, at different periods of time and in various sectors. It enables us to provide a scheme of the bathymetric distribution of Pteropods Thecosomes in the western Mediterranean Sea, as well as to try and draw a parallel between their localization and the nature of waters; the prospected area being very interesting from a hydrological and hydrodynamical point of view. The material, of diverse origins, comes from 84 deep fisheries and 19 corresponding surface ones, conducted between 1958 and 1966. It was exploited in two different ways: individual samples collected on 20 stations (fig. 1) in September ~ October 1958 and November 1963 resulted in a quantitative analysis from a geographical and bathymetrical point of view. The others, collected in 1961 and 1966, were only used to check the facts observed on the first ones. 1° The cruise conducted in autumn 1958 by the "Président-Théodore-Tissier", which lasted more than 3 weeks (27 September - 18 October), covered the entire region located north of the 42nd parallel and south-east of Corsica. Among the numerous stations equally distributed on this sector (1), 15 (fig. 1 and table 1) were 32 deep fisheries and 14 surface fisheries. The first ones, conducted with a "Schmidt" net, were carried out at different levels, down to more than 1 000 m (apart from stations 161 and 175 were bottoms do not reach 300 m) and as far as 2 760 m (table 1). 2° The 1963 cruise, carried out by the "Thalassa" on the 17th and 18th of November, dealt with 5 stations in the central western Mediterranean sector, between 40 and 42" degrees latitude north (fig. 1 et table 2); they were distributed on a NW-SE diagonal, at equal distances. On these five points, between 1 375 and 2 750 m deep, 18 fisheries were conducted using a "Discovery" net. We studied 16 of them, 5 of which were surface fisheries. Table 3 gives the different levels, between 0 and 2 000 m, at which the 1958 and 1963 fisheries were conducted. The observation of surface fisheries corresponding to deep samples enabled us, amongst others, to study the individuals' behaviour at nigh time....