(iv) The _Egypto-Syrian_ district extends along the south-eastern shores of the Mediterranean from Tripoli to North Syria, and eastward to the Euphrates valley. Lower Egypt alone belongs to this portion, the fauna of Upper Egypt being of an entirely tropical character, and belonging to the Ethiopian Region. _Lower Egypt._--The Mollusca of Lower Egypt stand in the unique position of belonging, half to the Palaearctic, and half to the Ethiopian Region. The land Mollusca are of a distinctly Mediterranean type, while the fresh-water, directly connected as they are by the great highway of the Nile with regions much farther south, contain a large admixture of thoroughly tropical genera (_Ampullaria_, _Lanistes_, _Melania_, _Cleopatra_, _Corbicula_, _Cyrena_, _Iridina_, _Spatha_, _Mutela_). The _Helices_, which are not numerous, are rather a mixture of circum-Mediterranean species than of a specially distinctive character. _H. desertorum_, however, belonging to the group _Eremophila_, is characteristic. There is a single _Parmacella_, but the physical features of the country are unfavourable to the occurrence of such genera as _Clausilia_, _Pupa_, _Hyalinia_, and the land operculates. _Syria._--The Mollusca, especially in the more mountainous regions of the north, are much more varied and numerous than those of Egypt. _Clausilia_ is again fairly plentiful, and the Helicidae are represented by some striking forms of the sections _Levantina_, _Pomatia_, and _Nummulina_. _Leucochroa_ has several curious types with a constricted aperture, and the Agnatha are represented by _Libania_, a peculiar form of _Daudebardia_. A prominent feature is the occurrence of a number of large white _Buliminus_ of the _Petraeus_ section (Fig. 200). Land operculates appear to be absent, but _Melanopsis_ and _Neritina_ are abundant. The Dead Sea contains no Mollusca, but Lake Tiberias has a rich fauna, including the above-mentioned genera, with a _Corbicula_ and several _Unio_. [Illustration: FIG. 200.--=A=, _Buliminus_ (_Petraeus_) _labrosus_ Oliv., Beyrout; =B=, _Buliminus_ (_Chondrula_) _septemdentatus_ Roth., Palestine.] _Upper Mesopotamia_ appears to possess a mixture of Syrian and Caucasian forms, including a _Parmacella_. Lower Mesopotamia has an exceedingly poor land fauna, but is comparatively rich in fresh-water species, the growing eastern character of which is shown by the occurrence of several _Corbicula_ and _Pseudodon_, and of a _Neritina_ of a distinctly Indian type.