ALBERT

Description: Sixty-six species of cephalopods are listed from South Africa from the area bounded on the east by Delagoa Bay and on the west by Luderitz Bay. Four new species are described and illustrated: Idiosepius biserialis, Idiosepius macrocheir, Inioteuthis capensis and Eledone thysanophora. In addition some of the species of cephalopods described by Robson from South Africa are redescribed or evaluated based on re-examination of the types in the British Museum. The history of cephalopod studies in South Africa is reviewed and all pertinent literature is cited.

Description: From a series of direct shear and laboratory vane shear tests conducted on natural pelagic and terrigenous marine soils, we have proposed a combined shear test procedure that involves obtaining the total stress failure envelope from tests on only two submarine soil samples. On one of the samples, both the direct shear and vane tests are conducted at zero normal stress. The second soil sample is consolidated under normal stress σn greater than the precompression stress Pc and sheared in a direct shear device under normal stress equal to the above consolidation pressure σn , the laboratory vane shear test on the same sample is conducted under zero normal stress. The combined test program results in four datum points (two from direct shear and two from laboratory vane shear tests. By connecting the two vane test datum points, the cohesion line (the failure envelope corresponding to vane shear tests) is obtained. By connecting the direct shear test datum points (from the soil consolidated under cn 〉 Pc) to the origin of the r vs. σn plane, the part of the failure envelope that lies beyond the precompression load is determined. The part of the failure envelope curve below the precompression stress is obtained by drawing a line parallel to the cohesion line through the direct shear datum point (corresponding to zero normal stress). The data and procedure reported herein indicate that the investigator can realize considerable time savings as well as conservation of sometimes expensive and limited submarine soil samples by using the proposed combined test procedure.