Egyptian Mollusca. 



As a preliminar}' to the systematic dissection of molluscs for 

 developmental stages of trematodes it was thou^^ht essential to 

 form a typical set of the various species of Egyptian Mollusca for 

 reference. Through the courtesy of Major Flower and Messrs. 

 Kicoll and Bonhote, we were given full liberty to make an 

 exhaustive examination of the various ponds in the Zoological 

 Gardens, Giza. These waters proved particularly rich in molluscan 

 fauna, and, as will be noticed from the localities given under each 

 species, provided typical examples of the bulk of the recorded 

 forms. 



^Molluscs are, generally speaking, essentially aquatic animals, 

 but a certain number are adapted to terrestrial life. The latter are 

 of interest in relation to these investigations only in so far as they 

 may be found living on the weeds overhanging the canals or dead 

 in the mud dredged for aquatic forms. A certain number which 

 came under our purview in this way are put on record. 



The larval metamorphosis of all digenetic trematodes occurs 

 without known exception in the bodies of molluscs belonging to 

 the classes Gastropoda and Lamellibranchia, which are comprised 

 in the grade Prorhipidoglossomorpha, and are alike distinguished 

 by the possession of a visceral commissure, a foot wholly posterior 

 to the head and a separation of direct communication between 

 gonads and pericardium. 



The large majority of trematode larvae develop in the Gastropoda. 

 The Gastropoda are specially characterized by a univalve shell, 

 an asymmetrical organization and a well-developed head, while the 

 Lamellibranchia have a bivalve shell, an internal and external 

 symmetry and a rudimentary cephalic region. 



The shells collected are described in accordance with the classi- 

 fication set out in the following table ; in every case the diagnosis 

 is provisional and is based upon a comparative study of the material 

 with the figures and description given by Pallary in his " Catalogue 

 de la Faune malacologiqne de I'Egypte," published in Cairo in 1900. 



