146 



MEDITERRANEAN PROVINCE. 



each forming a little cell ; and it is in the definite 

 shapes and modes of arrangement of these that 

 characters are found by which the multitudinous 

 assemblage of forms of Bryozoa can be systemati- 

 cally ordered. 



Not only is this class of animals of great assist- 

 ance in the determination of the relation of the 

 Mediterranean to surrounding faunas, but the 

 beauty and perfection in which their remains have 

 been preserved from the earliest times, aid us ma- 

 terially in interpreting the evidence of change 

 during the yet remoter past. M. A. D'Orbigny's 

 primary division of the Bryozoa is into two great 

 orders, — the Cellulinear, in which, to take outward 

 characters, the cells are arranged end to end, or 

 side to side ; and the Centrifuginous, in which the 

 cells spring from behind, or at the base of one an- 

 other. These two orders are by no means equally 

 represented among existing forms ; some few of the 

 latter occur in our European seas, but its repre- 

 sentatives have, for the most part, passed away. In 

 secondary and tertiary times, however, they swarmed 

 in the seas now occupied by our Celtic and Lusita- 

 nian zones. At present the forms of this order 

 have a wide distribution, and are known to reach 

 high northern or southern latitudes. Seriolaria 

 unilateralism S. convoluta, and S. lendigera are Lusi- 

 tanian and Mediterranean ; the latter is also Cel- 

 tic. Crisea eburnea has a great Atlantic range 

 as low as the Canaries. Cresidea cornuta is 



