الفهرس 
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Abstract
Family Vermetidae Rafinesque, 1815 is a group of Caenogastropoda whose taxonomy remains in a state of flux, despite two centuries of malacological studies. This is due in part to the resemblance of the shells to those of polychaetes serpulid, which has made the family an unpopular research subject. Little is known about the biology, ecology and geographical distribution of many of these wormlike gastropods and, for that matter, about the actual number of living species. The family Vermetidae comprises at least 160 extant species of sessile, suspension-feeding.
Marine gastropods of the family Vermetidae are sessile organisms with an irregular, uncoiled shell providing a three-dimensional biogenic habitat for associated species. Due to the irregular tube form; taxonomic identification has commonly been confused with Vermicularia (Turritellidae) Gastropoda and Serpulid polychaetes resulting in a confused taxonomic status. from the geological point of view vermetids are extremely reliable tools for interpreting past sea-level, sea temperature and productivity and consequently, of great importance for predicting future climatic trends.
On reviewing literature focusing on Vermetidae in the Middle East and to the best of the present authors` knowledge and as far as can be ascertained, few studies were carried out. The main objective of the present study was to make taxonomical studies on the vermetid mollusk Ceraesignum maximum inhabiting Red Sea coast of Egypt by carrying out the following points:
1.Identify the species using morphological and molecular studies.
2.Study the anatomy of the species as a helpful tool for its taxonomy and identification focusing on the digestive and reproductive systems. To achieve the above mentioned goals, Vermetidae species Ceraesignum maximum were collected during several collections from three different sites (I, II and III) on the Red Sea coast of Egypt. Some ecological factors including water temperature, pH, conductivity, salinity and TDS were measured during collecting time. Also several methods were used including dissection of the studied species, serial sections of the animal and using of scanning electron microscope to illustrate several structures like radula, operculum and the shell. The most important results of the study included the morphology of the species investigation. Also its anatomy including the digestive and reproductive systems was illustrated as helpful tools to identify the species. The study revealed that the general shape of the studied species is a tube like structure with the circular operculum situated in the anterior area in front of the mouth and attached to the muscle foot, the head with tentacles is bulbous in shape situated on the foot muscle, mantle cavity contain the osphradium, gills, rectum, pallial duct, and hypobranchial gland, the columellar muscle attached to the inner side of the tube, the stomach, digestive gland and reproductive area occupying the last third part of the animal body. The study revealed that sexes are separate and there is a sexual dimorphism which appears in the mantle slit in females. The reproductive system consists of: the gonads, vas deference, and pallial duct.
Scanning electron microscope was used to examine the shell coiling pattern and shell layer, radular tooth, and the operculum finger print shape. Protein gel electrophoresis was carried out to insure the identification and similarities of the collected specimen.